Scrambling for Dollars: International Liquidity, Banks and Exchange Rates∗
Javier Bianchi,† Saki Bigio,‡ and Charles Engel§
September 14, 2021
Abstract
We develop a theory of exchange rate fluctuations arising from financial institutions’ demand for liquid dollar assets. Financial flows are unpredictable and may leave banks “scrambling for dollars.” As a result of settlement frictions in interbank markets, a pre- cautionary demand for dollar reserves emerges and gives rise to an endogenous con- venience yield. In our framework, an increase in the volatility of idiosyncratic liquidity shocks leads to a rise in the convenience yield and an appreciation of the dollar—as banks scramble for dollars—while foreign exchange interventions matter because they alter the relative supply of liquidity in different currencies. We present empirical ev- idence on the relationship between exchange rate fluctuations for the G10 currencies and the quantity of dollar liquidity consistent with the theory.
Keywords: Exchange rates, liquidity premia, monetary policy JEL Classification: E44, F31, F41, G20
∗We would like to thank Andy Atkeson, Roberto Chang, Pierre-Olivier Gourinchas, Arvind Krishna- murthy, Martin Eichenbaum, Benjamin Hebert, Oleg Itskhoki, Matteo Maggiori, Dmitry Mukhin, Sergio Rebelo, Hel´ ene` Rey, and Jenny Tang for discussions. As well, we thank various conference participants. †Federal Reserve Bank of Minneapolis, email [email protected] ‡Department of Economics, University of California, Los Angeles and NBER, email [email protected] §Department of Economics, University of Wisconsin, Madison, NBER and CEPR, email [email protected] 1 Introduction
The well-known “disconnect” in international finance holds that foreign exchange rates show little empirical relationship to the supposed economic drivers of currency values, such as interest rates and output (Obstfeld and Rogoff, 2000). More recent work contends that the source of the disconnect is in financial markets (Itskhoki and Mukhin, 2021a). There long has been evidence of time-varying expected excess returns in foreign exchange markets, and, furthermore, it appears that the US dollar is particularly special, as it earns a premium over the rest of the major currencies when measured on historical data (Gourin- chas and Rey, 2007a). To account for the exchange rate disconnect and associated puzzles, the literature has turned to models with currency excess returns as the potential “miss- ing link”. The source or sources of these excess returns, however, remains an unsolved mystery. In this paper, we develop a theory of exchange rate fluctuations arising from the liquid- ity demand by financial institutions within an imperfect interbank market. We build on two observations on the international financial system. First, U.S. dollars are the dominant foreign-currency source of funding. According to the BIS locational banking statistics, in March 2021, the global banking and non-bank financial sector had cross-border dollar lia- bilities of over $11 trillion. Second, dollar funding may turn unstable. As documented for example in Acharya et al.(2017), banks are subject occasionally to large funding uncer- tainty or interbank market freezing that can leave them “scrambling for dollars.” Narrative discussions attribute fluctuations in the US dollar exchange rate to such vicissitudes in the short-term international money markets to. A contribution of our paper is to provide a framework to formally articulate this channel theoretically and to provide empirical evi- dence consistent with it. We construct a model in which financial institutions, which we simply refer to as banks, have a portfolio of assets and liabilities in two currencies. Banks face the risk of sudden outflows of liabilities. In case a bank ends up short of liquid assets to settle those flows, it needs to find a counterparty, but there may be times when banks may lose confidence in one another—this is the source of interbank market frictions. As insurance against these outflows, banks maintain a buffer of liquid assets—especially dollar liquid assets, in line with the aforementioned observations above on the international financial system. To the extent that uncertainty and the smoothness of interbank markets change over time, this increases the relative demand for currencies which translate into movements in the
1 exchange rate. The theory uncovers how frictions in the settlement of international deposit transac- tions emerge as a liquidity premium earned by the dollar. The liquidity premium gener- ates a time-varying wedge in the interest parity condition, or “convenience yield,” which plays a pivotal role in the determination of the exchange rate. Critically, the convenience yield is endogenous and depends on the quantity of outside money and policy rates in two currencies, as well as technology parameters such as matching efficiency in the interbank market, and the volatility of banking payments in different currencies. Through this en- dogenous convenience yield, we link the determination of nominal dollar exchange rates and the dollar liquidity premium to the reserve position of banks in different currencies, funding risk, and confidence in the interbank market. We provide empirical evidence consistent with the theory by relating the banking sec- tor’s balance sheet data to the foreign currency price of U.S. dollars. According to the theory, the financial sector increases its demand for dollar liquid assets—US government obligations, including reserves held at the Federal Reserve for banks in the Federal Reserve system—when funding becomes more uncertain, and in turn, this translates into an ap- preciation of the dollar. Our analysis shows that indeed the dollar liquidity ratio positively correlates with the relative value of the dollar. Notably, this relationship is robust to con- trolling for the VIX index, a variable that captures a broad measure of uncertainty, which has been shown to have significant explanatory power. The liquidity ratio is, of course, not an exogenous driver of exchange rates—either in our model or in the real world. However, we show that simulations of a calibrated version of our model implies a positive associa- tion between the change in the liquidity ratio and the value of the dollar under multiple driving shocks, including uncertainty shocks, monetary policy shocks, and liquidity de- mand shocks. Many recent theories have focused primordially on risk-premia or external financing premia to explain excess currency returns and exchange rate movements. Risk premium models explain excess dollar returns as stemming from a greater exposure of currencies other than the dollar to global pricing factors.1 External financing premium models ex- plain excess dollar returns as a funding advantage in dollar liabilities in the presence of limits to international arbitrage. We provide an alternative theory based on a liquidity premium. Our model abstracts, in fact, from risk premia and limits to international arbi-
1See, for example, Lustig et al.(2011, 2014).
2 trage to focus squarely on liquidity. At the center of the model is the idea that funding risk may leave banks scrambling for dollars. On the surface, the model resembles the seminal monetary exchange rate model of Lucas(1982). 2 In that model, two currencies earn a liquidity premium over bonds because certain goods must be bought with corresponding currencies. A money demand equation determines prices in both currencies, and relative prices determine the exchange rate. Our model shares the segmentation of transactions and the exchange-rate determination of Lucas. However, in our model, the demand for reserves in either currency stems from the settlement demand by banks. This distinction is important. First, because our model leads to predictions about the direction of exchange rates as functions of the ratio of reserves to deposits in different currencies, the size and volatility of flows in different currencies and the dispersion of interbank rates in different currencies. Second, because the policy implications are markedly different.
Literature Review
The expected excess return on foreign interest earning assets, or the deviation from “uncovered interest parity (UIP)" is important not just for understanding international pricing of interest-bearing assets, or the expected depreciation (or appreciation) of the currency, but also for the level of the exchange rate. This point is brought out clearly by Obstfeld and Rogoff(2003), which shows how the expected present value of current and future foreign exchange risk premiums affect the current exchange rate in a simple DSGE model. They refer to this present value as the “level risk premium.”3 Potentially, a better understanding of the role of ex ante excess returns can help account for the empirical failure of exchange-rate models (Meese and Rogoff, 1983; Obstfeld and Rogoff, 2000), and the excess volatility of exchange rates (Frankel and Meese, 1987; Backus and Smith, 1993; Rogoff, 1996). Much of the literature has been directed toward explaining the expected excess return as arising from foreign exchange risk. Another branch of the literature has explored limits to capital mobility and frictions in asset markets. A third branch has looked at deviations from rational expectations. A line of research closely related to this paper has been the role of the “convenience yield” in driving exchange rates. 2See also Svensson(1985) and Engel(1992a,b). 3This present value plays a key role in the analysis of Engel and West(2005), Froot and Ramadorai (2005), and Engel(2016). See Engel(2014)’s survey of exchange rates for an overview of the effect of the risk premium on exchange rates.
3 Foreign exchange risk premium. The modeling of failures of uncovered interest parity as arising from foreign exchange risk has a long history. Early contributions include Solnik (1974), Roll and Solnik(1977), Kouri(1976), Stulz(1981), and Dumas and Solnik(1995). Much theoretical work has been devoted toward building models of the risk premium that are consistent with the Fama(1984) puzzle, which finds a positive correlation between the expected excess return and the interest rate differential.4 Bansal and Shaliastovich(2013), Colacito(2009), Colacito and Croce(2011, 2013), Colacito et al.(2018b,a), and Lustig and Verdelhan(2007) examine models with recursive preferences. Verdelhan(2010) presents a model with habit formation to account for the Fama puzzle. Ilut(2012) proposes am- biguity aversion as a solution to the puzzle. Some recent studies, such as Burnside et al. (2011), Farhi and Gabaix(2016), and Farhi et al.(2015), model the risk premium as arising from risks associated with rare events. Recent empirical work sheds light on the nature of the foreign exchange risk premium. Lustig et al.(2014) identify a dollar risk factor that makes the dollar carry trade prof- itable. Hassan and Mano(2019) distinguish between the factors that drive the dollar carry trade and the cross-sectional deviations from uncovreed interest parity. Kalemli- Ozcan¨ (2019)and Kalemli- Ozcan¨ and Varela(2021) note that the factors driving risk pre- mia among advanced economies and emerging markets are different. An important development in the literature has been the modeling of the “safe haven” status of the U.S. dollar, and its association with the “exorbitant privilege” that the U.S. enjoys from the returns on its net foreign asset position. Gourinchas and Rey(2007a,b) re- port findings that the U.S. earns appreciably higher returns on its foreign investments than foreigners earn on investments in the U.S. Caballero et al.(2008) and Farhi and Maggiori (2018) offer models that help explain this phenomenon in which the U.S. is more able to “produce” safe assets that are valued by foreign investors but earn a lower expected return than foreign assets. Other papers have modeled the U.S. as a country that is willing to as- sume more risk, perhaps because its internal financial markets are more highly developed, and therefore are willing to hold riskier assets that yield a higher expected return (see, for example, Mendoza et al., 2009, Gourinchas et al., 2010, and Maggiori, 2017). Gourinchas et al.(2019) and Maggiori(2021) provide useful overviews of this literature. Recent research has focused on the interaction between risk-averse investors and habi- tat investors or noise traders who may not be motivated by risk/return considerations in
4See Tryon(1979) and Bilson et al.(1981) for earlier empirical studies that find this relationship. Engel (1996, 2014) surveys empirical and theoretical models.
4 their portfolio choice. These studies include Koijen and Yogo(2020) general model of portfolio choice, the preferred habitat models of Gourinchas et al.(2021), and Greenwood et al.(2020), and the noise trader model of Itskhoki and Mukhin(2021a,b). Limited Capital Mobility. Other models attribute these uncovered interest parity differ- entials to financial premia earned by foreign currency because of limited market partic- ipation as in models in which order flow matters for exchange rate determination also require some frictions in the foreign exchange market (see, for example Evans and Lyons (2002, 2008)). Relatedly, Bacchetta and Van Wincoop(2010) posit that slow adjustment of portfolios can account for the expected excess returns on foreign bonds. An important recent literature has emphasized limited market participation (see the segmented markets models of (Alvarez et al., 2009; Itskhoki and Mukhin, 2021a) or lim- ited international arbitrage (Gabaix and Maggiori, 2015; Amador et al., 2020; Itskhoki and Mukhin, 2021a).) This research has highlighted the role of financial intermediaries in helping to overcome barriers to asset trade, but underscored the balance sheet constraints of such institutions. While our model also brings financial intermediaries to the forefront, we do not introduce the collateral constraints or other limits to lending that has been the subject of these papers. The failure of covered interest parity since the global financial crisis is often interpreted as evidence of limits to arbitrage. See for example Baba and Packer(2009), Du et al.(2018), Avdjiev et al.(2019), Liao(2020), and the survey of Du and Schreger(2021). Our study offers an alternative channel by which deviations from covered interest parity might arise. Deviations from Rational Expectations. A simple alternative story for the UIP deviations is that agents expectations are not fully rational. Empirical studies, such as Frankel and Froot(1987), Froot and Frankel(1989), and Chinn and Frankel(2019) have used sur- vey measures of expectations to uncover possible deviations from rational expectations. Kalemli-Ozcan¨ (2019) and Kalemli- Ozcan¨ and Varela(2021) also find that the component of deviations from uncovered interest parity that is predictable from interest rate differen- tials may be driven by deviations from rational expectations. Models that incorporate systematically skewed expectations include Gourinchas and Tornell(2004) and Bacchetta and Van Wincoop(2006). Convenience Yield. Our model is closely connected to the recent examination of the “con- venience yield”—the low return on riskless government liabilities—and exchange rates. We posit that our model provides one possible channel for the emergence of the conve-
5 nience yield on U.S. government bonds. See Engel(2016), Valchev(2020), Jiang et al. (2020, 2021), Engel and Wu(2018), and Kekre and Lenel(2021) for recent work featur- ing simple, descriptive models of the convenience yield. In particular, Jiang et al.(2021) and Kekre and Lenel(2021) provide equilibrium models in which the appreciation of the dollar during times of global risk is driven by an increase in the convenience yield on the U.S. dollar. Our study might be described as providing the “microfoundations” for the convenience yield that provides a deeper understanding of the factors that might drive changes in the demand for U.S. dollar assets. Special role of the dollar. Our paper is related to the literature on the pre-eminence of the dollar in international financial markets. Rey(2013, 2016) and Miranda-Agrippino and Rey(2020) identify the importance of the US monetary policy as a key global factor in the global financial cycle. Gopinath(2016) and Gopinath et al.(2020) stress the domi- nating role of the dollar unit of account as one key possible channel. Gopinath and Stein (2021) link invoicing patterns and the safety of the dollar as a store of value. We propose a different channel based on the dominance of the dollar in the international financial system and argue that dollar liquidity shocks are a key drivers of exchange rates. The paper is organized as follows. Section2 presents the empirical analysis. Section3 presents the model and Section3 . Section5 presents the calibration of the model and the quantitative results. Section6 concludes. All proofs are in the appendix. 2 Empirical Analysis of Liquidity and Exchange Rates
We begin with a look at the data relating banking sector’s balance sheet and the foreign currency price of US dollars. Our thesis, at its simplest, is that the financial sector increases its demand for liquid dollar assets, including US government obligations and reserves held at the Federal Reserve, when funding becomes more uncertain and that this drives movements in exchange rates. Before we describe the data and our analysis, it is useful to provide some institutional background underlying the thesis. Institutional background. The US dollar serves as the leading funding currency. Close to half of all cross-border bank loans and international debt securities are denominated in dollars. In addition to serving as the key international unit of account, the dollar serves a vehicle currency for foreign exchange transactions as well as invoicing currency for global tradel. In fact, 85% of all foreign exchange transactions occur against the US dollar and
6 5 6 40% of international payments are made in US dollars. ˆ, The central role of the US dollar in the international financial and monetary system means that every day billions of US dollars circulate within and across countries. As the 2020 BIS working group report (Davies and Kent, 2020, p. 29) puts it:
US dollar funding is channeled through the global financial system, involving entities across multiple sectors and jurisdictions. Participants in these markets face financial risks typically associated with liquidity, maturity, currency and credit transformation. What makes global US dollar funding markets special is the broad participation of non-US entities from all around the world. These participants are often active in US dollar funding markets without access to a stable US dollar funding base or to standing central bank facilities which can supply US dollars during episodes of market stress.
The other pillar underlying our thesis is that financial institutions are subject to liquid- ity mismatch. To the extent that banks are not able to liquidate loans or other relatively illiquid assets, the demand of dollars by financial institutions can fluctuate considerably depending on funding conditions and vicissitudes of foreign exchange transactions. We will next argue how these conditions translate in the data into movements in the dollar exchange rates. Data and empirical analysis. We examine the behavior of the dollar against the other nine of the so-called G10 currencies, with special attention given to the euro. The euro area is especially important in our analysis because it encompasses a large economy with a financial system that relies heavily on short-term dollar funding. The other currencies are the Australian dollar, Canadian dollar, Japanese yen, New Zealand dollar, Norwegian krone, Swedish krona, Swiss franc, and the U.K. pound. We look at two sources of data for the US banking system. Detailed data on short- term dollar funding and on liquid dollar assets is not readily available for the global fi- nancial system, so we use the US data as a proxy for the dollar-denominated elements of the global banking balance sheets. That is, we presume that foreign banks’ demand for liquid dollar assets responds in a similar way to banks located in the U.S. (including U.S.- based subsidiaries of foreign banks) when faced with uncertainty about dollar funding.
5See Davies and Kent, 2020 and references therein. 6The global status of the US dollar dates to the Bretton Woods agreement, and more recently, this domi- nance has only deepened (Ilzetski, Reinhart and Rogoff).
7 This approach is also followed by Adrian et al.(2010), a study that aims to show how the price of risk is related to banks’ balance sheets and the expected change in the exchange rate (rather than the level of the exchange rate, which is our concern here), and presents a simple partial-equilibrium model of the banking sector. More precisely, Adrian et al. (2010) focuses on the state of the balance sheet at time t in forecasting et+1 − et, as they are concerned with understanding the expected excess return on foreign bonds between t and t + 1. Our interest is centered on how changes in the balance sheet between t − 1 and t contribute to changes in the exchange rate between t − 1 and t, that is et − et−1. We consider two measures of short-term funding to financial intermediaries. The first is used by Adrian et al.(2010), U.S. dollar financial commercial paper (series DTBSPCKFM from FRED, the Federal Reserve Economic Data website maintained by the Federal Re- serve Bank of St. Louis.) Another major source of short-term funding to U.S. banks is demand deposits, measured by DEMDEPSL from FRED. We construct a variable that mea- sures the level of funding and the response of financial intermediaries to uncertainty about that funding. We look at the ratio of the sum of reserves held at Federal Reserve banks and government (Treasury and agency) securities held by commercial banks (the sum of RES- BALNS and USGSEC from FRED) to short term funding (DTBSPCKFM + DEMDEPSL from FRED). This variable is endogenous in our model, but its movements are a key indi- cator of how the demand for dollars is affected by the financial sector’s demand for liquid assets when uncertainty increases. As dollar funding becomes more volatile for banks, they will increase their ratio of safe dollar assets to liabilities. That in turn will lead to a global increase in dollar demand, leading to a dollar appreciation. Figure1 plots this ratio of liquid government assets holdings to short-term funding of the financial sector.7 During this period, bank reserve balances rose from around 10 billion dollars in August, 2008 to nearly 800 billion dollars one year later, and then continued to climb to a peak of around 2.3 trillion dollars by late 2017 before gradually declining to 1.4 trillion dollars by the end of 2019. However, the liquidity ratio does not show movement anywhere near that magnitude. It is true that it rose during the onset of the global financial crisis, but this movement is not largely driven by the increase in reserves, because demand deposits rose almost proportionately. Mechanically, a large part of the rise in the overall liquidity ratio is driven by a fall in financial commercial paper funding, which works to lower the denominator of the ratio. 7The figure also plots an alternative measure described below.
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2001m1 0 1 2 3 4 ∆ iue1 h ai flqi sest hr-emliabilities short-term to assets liquid of ratio The 1: Figure e t 2003m7 epeetteprmtretmtso h regression: the of estimates parameter the present we 1, Table In ∆( = α x iudt ai AlternativeMeasureofLiquidityRatio Liquidity Ratio t + ) en h cag from “change the means β π 1 2006m1 e t ∆( t − i.e., , LiqRat π LiqRat t ∗ stedffrnebtenya-nya nainrtsin rates inflation year-on-year between difference the is β 2008m7 1 t + ) t oiie uigtmso ihucrany banks uncertainty, high of times During positive. hnw hudas xetapstv relationship positive a expect also should we then , β 2 ( 2011m1 9 π t − π t ∗ t + ) 2013m7 − β 1 3 8 to LiqDepRat h nainvral smeant is variable inflation The t ntevariable the in ” 2016m1 t − 1 2018m7 + t LiqRat x t ; e t t sthe is sthe is (1) hold greater amounts of liquid dollar assets (reserves and Treasury securities) relative to demand deposits, so LiqRatt is higher. That increased demand for safe dollar assets leads to a stronger dollar (an increase in et.)
We also include the lagged level of LiqRatt. This is included because the depreciation of the dollar might depend on lagged as well as current levels of this variable. The re- gressions we report would have the identical fit if we included current and lagged levels of this variable, instead of the change in the variable and the lagged level. We specify the regression as above for two reasons: First, specifying the regression so that the change in the liquidity variable influences the change in the exchange rate leads to a more natural interpretation. Second, while the current and lagged levels of the variable are highly cor- related, which leads to multicollinearity and imprecise coefficient estimates, the change and the lagged level are much less highly correlated. Table1 reports the regression findings for the nine exchange rates. The sample pe- riod is February 2001 to July 2020.9 (Data on financial commercial paper starts in January 2001.) With the exception of Japan, the liquidity ratio variable has the expected sign and is statistically significant at the 1 percent level for all exchange rates. The relative inflation variable also has the correct sign for all the currencies and is statistically significant for most countries It is commonplace to look at short-term interest rate movements to account for the ef- fects of monetary policy changes on exchange rates. During much of our sample period, interest rates were near the zero-lower bound, and do not appear to do a good job mea- ∗ suring the monetary policy stance. In the appendix, in Table A1, we include it − it , the interest rate in each of the 9 countries relative to the U.S. as regressors. It is only statis- tically significant at the 5 percent level for Japan, and none of the major conclusions are altered by its inclusion.
We highlight that the key regressor, ∆LiqRatt, is not simply a market price. That is, these regressions “explain” exchange rate movements but are not relying on other market prices to do the job. It is the balance sheet variables that play the pivotal role. We argue that uncertainty about funding drives the balance sheet variables, but what if we were to include a direct measure of uncertainty in the regressions? Many asset-pricing studies have used VIX to quantify market uncertainty, and VIX has power in explaining the movements of many asset prices. However, VIX does not directly measure uncer-
9Australia and New Zealand’s sample end in May 2020 because of availability of inflation data.
10 tainty about dollar funding for banks. Indeed, VIX might measure some dimensions of uncertainty, but it might also be capturing global risk, and global risk might be driving the dollar, as in the model of Farhi and Gabaix(2016). In Table2, we have included the change in VIX along with the other variables. As expected, VIX has positive coefficients in all cases (except Japan) and is statistically significant. An increase in VIX is associated with an appreciation of the dollar. However, the introduction of this variable does not reduce the significance of the liquidity ratio vari- able, for any of the countries, and for most only has a small effect on the magnitude of the coefficient. This suggests that the uncertainty that is quantified by the VIX does not in- clude all of the forces that drive the liquidity ratio and lead to its positive association with dollar appreciation. (Appendix table A2 also includes the interest rate differential, and as in Table A1, we see that its inclusion has little influence on the findings and its effect is mostly small and insignificant.) It is important to note that the liquidity ratio is not an exogenous driver of exchange rates—either in our model or in the real world. We will show that a calibrated version of our model implies a positive association between the change in the liquidity ratio and the value of the dollar under multiple driving shocks, including uncertainty shocks, monetary policy shocks and liquidity demand shocks. We can, however, use instrumental variables to isolate the effects of uncertainty on the liquidity ratio, and its transmission to exchange rates. To that end, Table3 uses two measures of uncertainty as instruments for the liquidity ratio: the cross-section standard deviation at each time period of the inflation rates of the G10 countries, and the cross- section standard deviation of the rates of depreciation for these currencies. The findings are largely the same as in Table2. For most of the countries, the magnitude of the effect of the liquidity ratio on the exchange rate is increased, and for some (such as Canada), the statistical significance greatly increases. The model still fits poorly for the Japanese yen, and we now find statistical significance of the liquidity ratio on the Swiss franc exchange rate. In appendix Table A3, we take the alternative tack of including VIX as an instrument for the liquidity ratio. It is possible for VIX to be a valid instrument that is uncorrelated with the regression error, even though it is statistically significant when included in the regression separately (as in Tables2 and3) if the other forces that drive the liquidity ratio are uncorrelated with VIX. That is, Table A3 reports the influence of the liquidity ratio on exchange rates when the liquidity ratio is driven by VIX and other measures of un-
11 certainty, while any other forces that might influence the exchange rate are relegated to the regression error. VIX is a valid instrument if it is uncorrelated with those forces. If one takes such a stance, then the estimates reported in Table A3 reveal a strong channel of uncertainty on exchange rates working through the liquidity ratio. We consider next an alternative measure of the liquidity ratio that includes “net financ- ing” of broker-dealer banks. This is a measure of “funds primary dealers borrow through all fixed-income security financing transactions,” as described in Adrian and Fleming(2005). We include this as another source of short-term liabilities, similar to how net repo financ- ing is included as a measure of short-term liabilities in the liquidity ratio calculated by the International Monetary Fund (Global Financial Stability Report, 2018). Figure1 also plots this alternative measure of the liquidity ratio, which is smaller than our baseline measure because it includes another class of liabilities of the banking system in the U.S. Tables A4, A5, A6, and A7 in the appendix are analogous to Tables1,2,3, and A3, re- spectively. The conclusions using this alternative measure are virtually unchanged quali- tatively, though of course the numerical values of the estimated coefficients are different. The liquidity ratio is still highly statistically significant for all currencies, except for Japan, and, in the case of the instrumental variable regressions, Switzerland. In Table4 we consider another dimension along which greater volatility in funding might affect banking behavior, which in turn can influence the exchange rate. In this table, we look at how the volatility of intra-day Fed funds rates are associated with the value of the dollar. We measure the volatility for a given month by taking the difference within each day between the high and the low transactions rates for that day, then taking the maximum of those differences over the month. Table4 reports instrumental variables regressions in which the instruments are the same as for Table3, and as in that table, we include VIX as a separate explanatory variable. We find that as the Fed funds volatility increases, the dollar tends to appreciate. This pattern holds across all dollar exchange rates, except for the Japanese yen and Swiss franc. In Table A8, as in Table A3, we include VIX as an instrument for the Fed funds volatility but not as an explanatory variable for the exchange rate, and we find a strong relation between the volatility measure and the value of the dollar.
12 Table 1: Exchange Rates and Liquidity Ratio Feb. 2001 – July 2020 EUR AUS CAN JPN NZ NWY SWE SWZ UK
∆(LiqRatt) 0.225*** 0.243*** 0.131*** -0.152*** 0.295*** 0.189*** 0.213*** 0.145*** 0.165*** (4.525) (3.597) (2.643) (-3.036) (4.302) (3.023) (3.555) (2.654) (3.320) ∗ πt − πt -0.542*** -0.422** -0.412* 0.008 -0.718*** -0.117 -0.492** -0.666*** -0.390** (-3.718) (-2.226) (-1.928) (0.055) (-3.757) (-0.803) (-2.521) (-2.803) (-2.114)
LiqRatt−1 0.011** 0.006 0.007 0.002 0.009 0.010* 0.006 0.005 0.009* (2.425) (1.065) (1.578) (0.315) (1.508) (1.763) (1.145) (0.990) (1.735) Constant -0.012*** -0.004 -0.006* -0.001 -0.009** -0.007* -0.009** -0.017*** -0.006 (-3.452) (-1.053) (-1.832) (-0.108) (-2.095) (-1.653) (-2.069) (-3.169) (-1.597) N 234 232 234 234 232 234 234 234 234 2 adj. R 0.11 0.05 0.03 0.03 0.10 0.03 0.05 0.04 0.04 t statistics in parentheses. * p < 0.1, ** p < 0.05, *** p < 0.01
Table 2: Exchange Rates and Liquidity Ratio and VIX Feb. 2001 – July 2020 EUR AUS CAN JPN NZ NWY SWE SWZ UK
∆(LiqRatt) 0.195*** 0.163*** 0.086* -0.137*** 0.232*** 0.139** 0.173*** 0.129** 0.140*** (3.999) (2.798) (1.909) (-2.741) (3.674) (2.358) (3.017) (2.337) (2.831) ∗ πt − πt -0.427*** -0.185 -0.277 -0.016 -0.519*** -0.032 -0.415** -0.595** -0.304* (-2.950) (-1.130) (-1.436) (-0.112) (-2.941) (-0.235) (-2.234) (-2.491) (-1.660)
∆VIXt 0.001*** 0.004*** 0.002*** -0.001** 0.003*** 0.002*** 0.002*** 0.001* 0.001*** (3.881) (9.339) (7.513) (-2.250) (6.909) (5.934) (5.153) (1.928) (3.116)
LiqRatt−1 0.011** 0.007 0.007* 0.002 0.009* 0.010* 0.007 0.005 0.008 (2.492) (1.427) (1.829) (0.334) (1.696) (1.892) (1.390) (1.063) (1.617) Constant -0.011*** -0.005 -0.006* -0.001 -0.009** -0.007* -0.008** -0.016*** -0.005 (-3.277) (-1.504) (-1.943) (-0.212) (-2.210) (-1.711) (-2.128) (-2.973) (-1.459) N 234 232 234 234 232 234 234 234 234 2 adj. R 0.16 0.31 0.22 0.05 0.25 0.16 0.15 0.05 0.07 t statistics in parentheses. * p < 0.1, ** p < 0.05, *** p < 0.01
13 Table 3: Exchange Rates and Liquidity Ratio Instrumental Variable Regression: StDev(Inf) and StDev(XRate) instrument for ∆(LiquidityRatio) Feb. 2001 – July 2020 EUR AUS CAN JPN NZ NWY SWE SWZ UK
∆(LiqRatt) 0.450*** 0.593*** 0.441*** -0.306** 0.507*** 0.526*** 0.473*** 0.019 0.717*** (3.150) (3.182) (3.274) (-2.266) (2.804) (2.831) (2.800) (0.121) (3.547) ∗ πt − πt -0.566*** -0.444** -0.496** 0.051 -0.658*** -0.242 -0.595*** -0.476 -0.981*** (-3.339) (-2.111) (-2.149) (0.328) (-3.250) (-1.370) (-2.728) (-1.640) (-3.034)
LiqRatt−1 0.014*** 0.013** 0.013** -0.002 0.013** 0.017** 0.011* 0.004 0.024*** (2.912) (2.119) (2.589) (-0.255) (2.123) (2.596) (1.897) (0.733) (2.922)
∆VIXt 0.001*** 0.003*** 0.002*** -0.001* 0.003*** 0.002*** 0.002*** 0.001** 0.000 (2.693) (6.879) (5.423) (-1.680) (5.659) (4.278) (3.971) (2.049) (0.856) Constant -0.015*** -0.010** -0.011*** 0.003 -0.012*** -0.013** -0.013*** -0.013* -0.017*** (-3.641) (-2.263) (-2.859) (0.433) (-2.645) (-2.528) (-2.708) (-1.834) (-2.896) N 234 232 234 234 232 234 234 234 234
t statistics in parentheses. * p < 0.1, ** p < 0.05, *** p < 0.01
Table 4: Exchange Rates and Measure of Intraday Fed Funds Rate Dispersion Instrumental Variable Regression: StDev(Inf) and StDev(XRate) instrument for ∆(MaxDift) EUR AUS CAN JPN NZ NWY SWE SWZ UK
∆(MaxDift) 0.013** 0.016** 0.011*** -0.006 0.013* 0.013** 0.014** 0.000 0.018*** (2.166) (2.358) (2.707) (-1.486) (1.908) (2.165) (2.067) (0.049) (2.725) ∗ πt − πt -0.493* -0.345 -0.046 0.028 -0.671** -0.003 -0.696* -0.518 -0.370 (-1.811) (-1.161) (-0.195) (0.201) (-2.241) (-0.014) (-1.968) (-1.249) (-1.217)
MaxDift−1 0.005* 0.006* 0.004* -0.005** 0.007* 0.005 0.007* 0.001 0.008** (1.680) (1.667) (1.736) (-2.302) (1.781) (1.507) (1.846) (0.222) (2.224)
∆VIXt 0.001** 0.004*** 0.002*** -0.001* 0.003*** 0.002*** 0.002*** 0.001** 0.000 (1.977) (4.636) (4.332) (-1.660) (3.867) (2.851) (2.803) (2.222) (0.260) Constant -0.013* -0.011* -0.007 0.008* -0.015** -0.009 -0.019** -0.013 -0.013* (-1.821) (-1.686) (-1.618) (1.673) (-2.013) (-1.351) (-2.003) (-1.085) (-1.859) N 187 187 187 187 187 187 187 187 187
t statistics in parentheses. * p < 0.1, ** p < 0.05, *** p < 0.01
14 3 A Model of Banking Liquidity and Exchange Rates
We present a dynamic equilibrium model of global banks that intermediate international financial flows and are subject to idiosyncratic liquidity shocks. The model has two coun- tries, the EU and the US, with corresponding currencies. To fix ideas, we think about the euro as the domestic currency and the dollar as the foreign currency. In each country, there is a continuum of households and a central bank that sets monetary policy. Produc- tion of the single tradable good is carried out globally by multinationals. We assume the law of one price. 3.1 Environment
Timing. Time is discrete and there is an infinite horizon. Every period is divided in two sub-stages: a lending stage and a balancing stage. In the lending stage, banks make their equity payout, Divt, and portfolio decisions. In the balancing stage, banks face liquidity shocks and re-balance their portfolio. Notation. We use “‘asterisk” to denote the foreign currency (i.e., the “dollar”) variable and “tilde” to denote a real variable. The vector of aggregate shocks is indexed by X. The exchange rate is defined as the amount of euros necessary to purchase one dollar—hence, a higher e indicates an appreciation of the dollar. Preferences and budget constraint. Payouts are distributed to households that own bank shares and have linear utility with discount factor β. Banks’ objective is to maximize share- holders’ value and therefore they maximize the net present value of dividends:
∞ X t β · Divt. (2) t=0
Banks enter the lending stage with a portfolio of assets/liabilities and collect/make asso- ciated interest payments. The portfolio of initial assets is given by liquid assets mt, both in euros and dollars, and corporate loans, bt, denominated in consumption goods. Note that we refer to liquid assets as “reserves”, for simplicity, but they should be understood as capturing also government bonds—the important property, as we will see, is that these are assets that can be used as settlement instruments. On the liability side, banks issue demand deposits, dt, discount window loans, wt, and net interbank loans, ft (if the bank has borrowed funds, ft is positive, and vice versa), again in both currencies. Deposits and
15 interbank market loans have market returns given by id and ¯if while central banks set the m w corridor rates for reserves and discount window, respectively i and i . A yield it paid in period t is pre-determined in period t − 1. Meanwhile, Rb is the real return on loans. The bank’s budget constraint is given by
∗ mt+1 − dt+1 ∗ ∗ ∗ ∗ b ∗ m,∗ ∗ d,∗ Pt Divt + + bt+1Pt + mt+1 − dt+1 ≤ Pt btRt + mt (1 + it ) − dt (1 + it ) et m d f w ∗ f,∗ ∗ w,∗ mt(1 + it ) − dt(1 + it ) + ft(1 + it ) + wt(1 + it ) + ft (1 + it ) + wt (1 + it ) − . (3) et
Withdrawal shocks. In the balancing stage, banks are subject to random withdrawal of de- posits in either currencies. As in Bianchi and Bigio(2021), withdrawals have zero mean— hence deposits are reshuffled but preserved within the banking system. In addition, we assume that the distribution of these shocks is time-varying: As a way to capture the spe- cial role of the dollar in wholesale funding and other volatile funding sources of funding, as discussed in Section2. In particular, withdrawal shocks, denoted by ω, have a CDF denoted by Φt—PDF denoted by φt. The inflow/outflow of deposits across banks generates, in effect, a transfer of liabilities. We assume that these transfer of liabilities are settled using reserves of the corresponding currency. Importantly, reserves must remain positive at the end of the period. We denote j j by s the euro surplus of a bank facing a withdrawal shock ωt . This surplus is given by the amount of euro reserves a bank brings from the lending stage minus the withdrawals of deposits: j j st = mt+1 + ωt dt+1. (4)
We omit the subscript of bank choices in deposits and reserves, because it is without loss of generality that all banks make the same choices in the lending stage. If a bank faces a negative withdrawal shock, lower than ω˜ ≡ −m/d, the bank has a deficit of reserves. Conversely, if the withdrawal shock is larger than ω˜, the bank has a surplus. Notice that if m = 0, the sign of the surplus has the same sign as the withdrawal shock. A higher liquidity ratio makes more likely that the bank will be in surplus. Similarly, we have the following surplus in dollars
j,∗ ∗ j,∗ ∗ st = mt+1 + ωt dt+1. (5)
16 Interbank market. After the withdrawal shocks are realized, there is a distribution of banks in surplus and deficits in both currencies. We assume that there is an interbank for each currency in which banks that have a deficit in one currency borrow from banks that have a surplus in the same currency. These two interbank market behave symmetri- cally, so it suffices to show only how one of the markets work.10 We model the interbank market as an over-the-counter (OTC) market, in line with in- stitutional features of this market (see Ashcraft and Duffie, 2007; Afonso and Lagos, 2015). Modeling the interbank market using search and matching is also natural considering that the interbank market is a credit market in which banks on different sides of the market— surplus and deficit—must find a counterpart they trust. As a result of the search frictions, only a fraction of the surplus (deficit) will be lent (borrowed) in the interbank market. We assume, in particular, that each bank gives an order to a continuum of traders to either lend or borrow, as in Atkeson et al.(2015). A bank with surplus s is able to lend a fraction Ψ+ to other banks. The remainder fraction is kept in reserves. Conversely, a bank that has a deficit is able to borrow a fraction Ψ− from other banks, and the remainder deficit is borrowed at a penalty rate iw. The penalty rate can be thought of as the discount window rate or as an overdraft-rate charged by correspondent banks that have access to the Fed’s discount window. The fractions Ψ+and Ψ− depend on the abundance of reserve deficits relative to sur- pluses. Assuming a constant returns to scale matching function, the probabilities depend entirely on market tightness, defined as
− + θt ≡ St /St (6)
+ 1 j − 1 j where St ≡ 0 max st , 0 dj and St ≡ − 0 min st , 0 dj denote the aggregate surplus ´ ´ and deficit, respectively. Notice that because m ≥ 0 and E(ω) = 0, we have that in equi- librium θ ≤ 1. That is, there is a relatively larger mass of banks in surplus than deficit. The interbank market rate is the outcome of a bargaining problem between banks in deficit and surplus, as in Bianchi and Bigio(2021). There are N trading rounds, in which banks trade with each other. If banks are not able to match by the N trading rounds, they deposit the surplus of reserves at the central bank or borrow from the discount window.
10We are assuming in the background an extreme form of segmented interbank markets: penalties in dollars and euros are independent because dollar surpluses cannot be used to patch Euro deficits and vice versa. This assumption can be relaxed to some extent but some form of segmentation of asset markets is necessary to obtain liquidity premia. See the discussion below.
17 Throughout the trading, the terms of trade at which banks borrow/lend, i.e., the interbank market rate, depend on the probabilities of finding a match in a future period. We denote f by i the average interbank market rate at which banks trade on average. Ultimately, we can define a real penalty function χ that captures the benefit of having a real surplus or deficit s˜ upon facing the withdrawal shock as follows: + 0 0 χ (θ; X,X )˜s if s˜ ≥ 0, χ(θ, s˜; X,X ) = (7) χ−(θ; X,X0)˜s if s˜ < 0
where χ+ and χ−are given by
− 0 w 0 m 0 − w 0 f 0 χ (θ; X,X ) = [R (X,X ) − R (X,X )] − Ψ (θ)[R (X,X ) − R (X,X )] (8) + 0 + f 0 m 0 χ (θ; X,X ) = Ψ (θ)[R (X,X ) − R (X,X )]. (9)
y 0 1+iy(X) In these expressions, R (X,X ) ≡ 1+π(X,X0) , denote the realized gross real rate of an as- 0 P (X0) set/liability y and π(X,X ) ≡ P (X) − 1 denotes the inflation rate when the initial state is X and the next period state is X0. When it does not lead to confusion, we streamline the h y i 0 ¯y 1+i (X) argument (X,X ) in these expressions. We also denote by R ≡ E 1+π(X,X0) |X as the ex- pected real rate—recall that the nominal rate is pre-determined but the ex-post real return depends on the inflation rate. Equation (8) reflects that a bank that borrows from the the interbank market or from the discount window, obtains the interest on reserves—hence the cost of being in deficit is given by Rf − Rm in the former and Rw − Rm in the latter. By the same token, (9) reflects that the benefit from lending in the interbank market in case of surplus is Rf − Rm. Figure2 present a sketch of the timeline of decisions within each period. We next turn to describe the bank optimization problem. Banks’ problem. The objective of a bank is to choose dividends and portfolios to max- imize2 subject to the budget constraint. Critically, when choosing the portfolio, banks anticipate how withdrawal shocks may lead to a surplus or deficit of reserves and asso- ciated costs and benefits. We express the bank’s optimization problem in terms of real portfolio holdings {˜b, m˜ ∗, d˜∗, d,˜ m˜ } and the real returns. For example, we define for exam- ple m˜t ≡ mt/Pt−1. The problem can be expressed recursively as follows:
18 FX openFX close
ω Portfolio OTC Settlements Average Choices Shock Market Market Payouts (m∗, b∗, d∗, m, b, d) R,¯ Ψ+, Ψ− (χ+, χ−)
Figure 2: Timeline
Problem 1. The recursive problem of a bank is
0 0 v (n, X) = max Div + βE [v (n ,X ) |X] (10) {Div,˜b,m˜ ∗,d˜∗,d,˜m˜ } subject to the budget constraint:
∗ ∗ Div+˜b +m ˜ +m ˜ = n + d˜+ d˜ , (11) where the evolution of bank networth is given by,
n0 = Rb(X)˜b + Rm(X,X0)m ˜ + Rm,∗(X,X0)m ˜ ∗ − Rd(X,X0)d˜− R∗,d(X,X0)d˜∗ | {z } Portfolio Returns ∗ ∗ ∗ ∗ ∗ 0 0 + χ (θ (X), m˜ + ω d˜ ; X,X ) + χ(θ(X), m˜ + ω d˜; X,X ) . (12) | {z } Settlement Costs
The variable n represents the banks’ net worth at the beginning of the period.11 The bank n o then chooses the portfolio ˜b, m˜ ∗, d˜∗, d,˜ m˜ and its dividends Div to maximize the future value. The evolution of n depends on the realized return on assets, but also on the re- alized settlement costs. Because of the linearity of the banks’ payoffs and the objective function, the value function is linear in net worth. An equilibrium with a finite supply of
11To obtain (12), we use the definition of χ as expressed in (7)-(9) and the real returns. Implicit in the law of motion for net worth is the convention that a bank that faces a withdrawal covers the associated interest payments net of the interest on reserves.
19 loans, deposits and reserves requires that Rb (X) = 1/β ≥ Rm (X,X0) .12 The next lemma characterize the solution of the bank under this result. Lemma (1) summarizes these results: Lemma 1. The solution to (10) is v (n, X) = n, and the optimal portfolios solve
? b 0 ∗,d 0 ˜∗ b ∗,m ∗ Π (X) = max EX0 R (X,X ) − R (X,X ) d − R (X) − R (X) m˜ {m,˜ d˜∗,d,˜m˜ } + Rb(X,X0) − Rd(X,X0) d˜− Rb(X,X0) − Rm(X,X0) m˜ h ∗ ∗ 0 ∗ ∗ ˜∗ 0 i h 0 ˜ 0 i + Eω∗ χ (θ (X,X ), m˜ + ω d ; X,X ) + Eω χ(θ(X,X ), m˜ + ω d; X,X ) . (13)
In equilibrium, Π(X) = 0.
Central to this optimization problem are the liquidity costs, as captured by χ and χ∗. Deposits in either currency have direct interest costs given by the real returns on deposits, but also affect indirectly the banks’ settlement needs. Reserves in each currency yield direct real returns, correspondingly, but have the additional indirect benefit of leading to higher average positions in the interbank market. It is important to note that the bank problem is homogeneous of degree one: As a result, the scale of dollar and euro deposits of each bank is indeterminate for an individ- ual bank. The liquidity ratio and the leverage ratio, however, are not. In effect, the kink in the liquidity cost function creates concavity in the bank objective, generating interior solutions for the ratios.13 Thus, liquidity risk generates an endogenous bank risk-averse behavior, which will be critical for the determination of the exchange rate, as will become clear below. Importantly, at the individual level, the liquidity ratio and the leverage ratio are deter- mined. This is not the case, however, for dividends and the scale of the portfolio, which are are determined only at the aggregate level. In particular, {n, Div} must guarantee that the quantity of loans be consistent with Rb = 1/β and zero expected profits, Π(X) = 0. Non-Financial Sector. This section presents the description of the non-financial block: This block is composed of a representative household, one in each country. Households
12If the return on loans were lower than 1/β, banks would not invest in loans. Conversely, if the return on loans were higher than 1/β,banks would inject infinite equity in the bank. If Rm > 1/β banks would issue equity to buy reserves and the bank’s value would be indeterminate. 13This behavior is analogue to the behavior of productive firms with Cobb-Douglas technologies: firms earn zero-profits, their production scale is indeterminate, but the ratio of production inputs is determined in equilibrium as a function of relative factor prices.
20 supply labor and save in deposits in both currencies. Firms are multinationals which use labor for production and are subject to working capital constraints, giving rise to a demand for loans. This block delivers an endogenous demand schedule for loans, and deposit de- mands in both currencies. To keep the model simple, we make assumptions so that the effective loan demand and deposit supplies are static. As we show in AppendixC, we obtain the following schedules:
¯b b b Rt+1 = Θ (Bt) , < 0, Θt > 0, (14) ¯∗,d ∗,d ∗,s ς∗ ∗,d Rt+1 = Θ (Dt ) , ς > 0, Θ > 0, and (15) ¯d d s ς d Rt+1 = Θ (Dt ) , ς > 0, Θ > 0, (16) where is the semi-elasticity of credit demand and {ς, ς∗} are the semi-elasticities of the deposit supplies with respect to the real returns. These parameters are linked to the pro- duction structure and preference parameters in the micro-foundation. m Government/Central Bank. Both central banks choose the rates for reserves it and dis- w ∗ count window it . Central banks in each country also set the supply of reserves Mt+1,Mt+1 . To balance the payments on reserves and the revenues from discount window loans, we assume that central banks use lump sum taxes/transfers rebated to households from the same country. Because households have linear utility in the tradable consumption good, these lump sum taxes only affect the level of consumption, but have no other implications. Using Wt to denote the discount window loans, we have the following budget constraint for the domestic economy,
m w Mt + Tt + Wt+1 = Mt−1(1 + it ) + Wt(1 + it ). (17)
An identical budget constraint holds for the foreign economy. In both countries Tt adjusts to passively to balance the budget constraint, given the monetary policy choices. 3.2 Equilibrium
We study recursive competitive equilibria where all variables are indexed by the vector of aggregate shocks, X. We consider shocks to the nominal interest rates on reserves, the deposit supply, and the volatility of withdrawals. Without loss of generality, we restrict to a symmetric equilibrium, in which all banks choose the same portfolios.
Definition 1. Given central bank policies for both countries {M(X), im(X), iw(X),W (X)},
21 {M ∗(X), im,∗(X), iw,∗(X),W ∗(X)} a recursive competitive equilibrium is a pair of price level functions {P (X),P ∗(X)}, exchange rates e(X), real returns for loans, Rb(X), nomi- f nal returns for deposits {id(X), id,∗(X)}, an interbank market rate i (X), market tightness θ(X), bank portfolios {d(X), d∗(X), m(X), m∗(X), ˜b(X)}, interbank and discount window loans {f(X), f ∗(X), w(X), w∗(X)} and aggregate quantities of loans {B˜(X)} and deposits {D(X),D∗(X)} such that:
(i) Households are on their deposit supply and firms are on their loan demand. That is, equations (14)-(16) are satisfied given real returns and quantities {B˜(X),D(X),D∗(X)}.
(ii) Banks choose portfolios {d˜(X), d˜∗(X), m˜ (X), m˜ ∗(X), ˜b(X)} to maximize expected prof- its, as stated in (13).
(iii) The law of one price holds P (X) = P ∗(X)e(X).
(iii) All market clear: The deposit markets: d˜(X) = Ds,(X) and d˜∗(X) = Ds,∗(X). The reserve markets: m˜ (X) P (X) = M(X) and m˜ ∗(X)P ∗(X) = M ∗(X). The loans market: ˜b(X) = B(X). The interbank market: Ψ+(X)S+ = Ψ−(X)S−.
(vi) Market tightness θ(X) is consistent with the portfolios and the distribution of with- drawals while the matching probabilities {Ψ+(X), Ψ−(X)} and the fed funds rate f i (X) are consistent with market tightness θ.
Combining both equations in reserve-market clearing conditions, and the law of one price and the deposit clearing conditions, we arrive at a condition for the determination of the nominal exchange rate:
P (X) M(X)/m˜ (X) M(X)/D (X) /m˜ (X)/D (X) e(X) = = = . P ∗ (X) M ∗(X)/m˜ ∗(X) M ∗(X)/D (X) /m˜ ∗(X) (18)
Condition (18) is a Lucas-style exchange rate determination equation, but rather than fol- lowing from cash-in-advance constraints these follow from bank portfolio decisions link- ing liabilities with reserve assets. Given a real demand for reserves in euro and dollars that emerge from the bank portfolio problem (13), the dollar will be stronger (i.e., higher e) the larger is the nominal supply of euro reserves relative to dollar reserves. Similarly, for given nominal supplies of euro and dollar reserves, the dollar will be stronger the larger is the demand for real dollar reserves.
22 The novelty here relative to the canonical model is that liquidity factors play a role in the real demand for currencies, and hence affect the value of the exchange rate. We turn next to analyze this mechanism. 4 Characterization
Liquidity Premia and Exchange Rates. To understand how liquidity affects exchange rates, we inspect the portfolio problem (13). Using (7), we write the expected profits of a bank with portfolio (m, m∗, d, d∗) as follows:
∗ b ∗,d ∗ b ∗,m ∗ Π (X) = R¯ − R¯ d˜ − R¯ − R¯ m˜ + (19) R¯b − R¯d d˜− R¯b − R¯m m˜ + −m∗/d∗ ∞ χ∗,−(θ) (m ˜ ∗ + ω∗d˜∗)dΦ∗(ω∗) + χ∗,+(θ) (m ˜ ∗ + ω∗d˜∗)dΦ∗(ω∗)+ ˆ−1 ˆ−m∗/d∗ −m/d ∞ χ−(θ) (m ˜ + ωd˜)dΦ(ω) + χ+(θ) (m ˜ + ωd˜)dΦ(ω). ˆ−1 ˆ−m/d
The first two lines are the excess returns on loans relative to deposits and reserves. The last two lines represent the expected liquidity costs in both currencies. The first-order condition with respect to m∗ is
¯b ¯m,∗ ∗ ∗ ∗ +,∗ ∗ ∗ ∗ −,∗ ∗ ∗ ∗ R − R = (1 − Φ (−m /d ))χ (θ ) + Φ(−m /d )χ (θ ) = Eω∗ [χm∗ (s ; θ )] . (20)
At the optimum, banks equate the expected marginal return of making loans, R¯b, with the marginal return on reserves. The latter is given by the interest on reserves R¯m plus a random marginal liquidity value. If the bank ends up in surplus, which occurs with probability 1 − Φ(−m∗/d∗), the marginal value is χ+,∗ and if the bank ends up in deficit which occurs with probability Φ(−m∗/d∗), the marginal value is χ−,∗. Given {χ+,∗, χ−,∗} a higher ratio of reserves to deposits is associated with a smaller R¯b − R¯m premium. We label this difference as the bond premium, BP ≡ R¯b − R¯m. We have an analogous condition for m:
¯b ¯m + − R = R + (1 − Φ(−m/d))χ (θ) + Φ(−m/d)χ (θ) = Eω [χm (s; θ)] . (21)
23 Combining (20) and (21), we obtain a condition that relates the difference in the real return on reserves on both currencies:
¯m ¯m,∗ ∗ ∗ R − R = Eω∗ [χm∗ (s ; θ )] − Eω [χm (s; θ)] . (22) | {z } LP
We label this difference, the dollar liquidity premium (LP), LP ≡ R¯m − R¯∗,m. Using that 1 + π = (1 + π∗)e0/e and the law of one price, we express (22) as: 1 m m,∗ et+1 Et 1 + it − (1 + it ) · = LP. (23) 1 + πt+1 et This is an uncovered interest parity condition (UIP) adjusted by a liquidity premium. Absent a liquidity premia, (23) would reduce to a canonical UIP that simply equates, to a first order, the difference in nominal returns to the expected depreciation. However, whenever the marginal liquidity value of a dollar is larger than the marginal liquidity value of a euro (i.e.,. when the LP is positive), and the nominal rates are equal, this implies that the dollar must be expected to depreciate. This way, the dollar reserve delivers a lower expected real return compensating for the higher liquidity value. Because banks are risk neutral, there is no risk premiumand the UIP emerges entirely through liquidity. Finally, we have the first-order conditions with respect to deposits in both currencies:
¯d ¯m R = R + Eω [χm (s; θ)] + Eω [χd (s; θ)] and (24) ¯d,∗ ¯m,∗ ∗ ∗ ∗ ∗ R = R + Eω∗ [χm∗ (s ; θ )] + Eω∗ [χd∗ (s ; θ )] . (25)
The four first-order conditions, together with the bank’s budget constraint, characterize the bank’s portfolio decision. Couple with the demand-supply system, this equations fully characterize the equilibrium. Funding and Payment Volatility shocks. We now provide a theoretical characterization of how the exchange rate and the liquidity premia vary with shocks. In this section, we assume that the supply of deposits are perfectly inelasticto sharpen the results, while not altering the essence of the model. Here we present exact formulas for permanent and iid shocks, and relegate approximate results for more general AR(1) shocks to AppendixB which contains all the proofs. We focus on shocks to the dollar. The same shocks to the euro interbank market will carry the opposite effect on the exchange rate and the LP. Throughout the results, a useful
24 object for the characterization is the liquidity ratio which, defined in terms of aggregates, M/P is given by µ ≡ D . A critical object in the characterization is the derivative of the LP with respect to θ∗:
∗ ∗ ∗,+ ∗ ∗ ∗,− LPθ∗ = (1 − Φ (−µ )) · χθ∗ + Φ (−µ ) · χθ∗ > 0.
We proceed to discussing the effects of various shocks. First, we characterize the effects shocks to the supply of dollar deposits.
Proposition 1 (Deposit scale effects). Consider a shock that increases the real supply for dollar deposits, D∗. 1) If the shock is temporary and (iid) it appreciates the dollar, reduces the dollar liquidity ratio, and increases the premia:
∗ ∗ ∗ d log e d log P −LPθ∗ · θµ · µ ∗ = − ∗ = b ∗ ∗ ∈ [0, 1), d log D d log D R − LPθ∗ · θµ · µ
∗ b d log µ R ∗,m ∗ = − b ∗ ∗ ∈ [−1, 0), and dBP = dLP = R d log e. d log D R − LPθ∗ · θµ · µ
2) If the shock is permanent (random walk) it appreciates the dollar one for one and is neutral on the liquidity ratio and the premia:
d log e∗ d log P ∗ = − = 1, and dµ∗ = dBP = dLP = 0. d log D∗ d log D∗
Proposition1 establishes that a higher supply of dollar deposits appreciate the dollar. The logic is simple: a higher amount of real dollar deposits increases the demand for real dollar reserves. Given a fixed nominal supply, we must have an appreciation of the dollar. There is an important distinction between temporary and permanent shocks. When the shock is temporary, the exchange rate is expected to revert to the initial value in the following period. Given nominal rates, this reduces the expected real return of holding dollar reserves. As a result, the demand for real dollar reserves fall. In equilibrium, the increase in the scarcity of dollar reserves leads to an increase in the LP. Overall, we then have that in response to an increase in the supply of dollar deposits by households, the dollar appreciates, the dollar liquidity ratio falls, and the LP increases.
25 When the shock is permanent, the effect on the exchange rate is expected to be perma- nent. Absent any expected depreciation effects, the dollar liquidity ratio remains constant. As a result, there are no permanent effects on the LP.14 Next, we characterize the effects of a rise in payment dispersion of dollar deposits. For that purpose, it is useful to index Φ by a parameter that captures the payment dispersion, σ. We also define notation for the mass of surplus payment shocks:
∞ δ∗ (µ∗, σ∗) ≡ ωφ (ω; σ∗) dω. ˆµ∗
We maintain the following assumption:
∗ ∗ ∗ Assumption 1. Any right tail of Φ is increasing in σ , i.e. δσ∗ > 0 for any µ .
This assumption is enough to characterize the effects of payment volatility shocks.
Proposition 2 (Volatility effects). Consider a shock that increases the size of dollar payment shocks, σ∗. 1) If the shock is temporary (iid) it appreciates the dollar, raises the dollar liquidity ratio and raises the :
∗ ∗ ∗ ∗ d log e d log µ d log P LPσ∗ σ 1 − θ δσ∗ ∗ = ∗ = − ∗ = b ∗ ∈ 0, · ∗ , and d log σ d log σ d log σ R − LPµ∗ · µ 1 + θ µ
dBP = dLP = R∗,md log e.
2) If the shock is permanent (random walk). Then, the shock appreciates the dollar, raises the liquidity ratio:
∗ ∗ ∗ d log e d log µ d log P 1 − θ δ ∗ = = − ∈ 0, · σ , and dBP = dLP = 0. d log σ∗ d log σ∗ d log σ∗ 1 + θ µ∗
Proposition2 presents a central result. In response to a rise in the volatility of dollar payments, the dollar appreciates, and there is an increase in the dollar liquidity ratio and the LP. Intuitively, with a larger dollar volatility, banks demand greater real dollar re- serves. With the nominal supplies given, this must lead to an appreciation of the dollar.
14This neutrality result hinges on the assumption of constant returns to scale in the interbank matching technology. As banks scale up proportionally dollar deposits and reserves, given the same real returns on dollar and euro reserves, the original liquidity ratio remains consistent with the new equilibrium.
26 Again, there is a relevant distinction between temporary or permanent shocks. When the shock is temporary, the expected depreciation of the dollar reduces the expected real re- turn of holding dollar reserves. Given the nominal rates, this implies that the LP must be larger in equilibrium for (23) to hold. When the shock is permanent, the volatility shock appreciates the dollar without any effects on the liquidity ratio or the LP. The result in Propositions1 and2 highlight that episodes of large supply of dollar deposits and high dollar volatility and go hand in hand with appreciations of the dol- lar. The proposition characterizes the effects of payments volatility under iid shocks and random-walk shocks and perfectly inelastic deposit supplies, but the effects hold for mean- reverting processes and general elasticities. Based on a calibration to be described below, Figure3 shows endogenous variables as a function of the volatility of the withdrawal of dollar deposits.15 In line with the results of Proposition2, we can see that a higher volatility appreciates the dollar (panel [a]) and lowers the expected return on dollar bonds relative to euros (panel [b]), reflecting the larger dollar liquidity premium. In addition, we can see a rise in the differential rate on deposits (panel [e]). That is, the rate on euro deposits increases relative to the dollar rate as the rise in volatility makes euro deposits more at- tractive. Furthermore, there is a rise in the loan rate because higher volatility increases, in effect, the liquidity frictions and reduces the demand for loans. Finally, we also see an increase in the dollar liquidity ratio concomitantly with a reduction in the euro liquidity ratio. The latter occurs because a higher lending rate makes euro reserves relatively less attractive (in the absence of any shocks to the euro market). Another message from the propositions is that the convenience yield of the dollar is linked to the payment volatility of the dollar, but not the size of dollar per se. To see this point, observe that the effects of permanent shocks in Propositions1 and2 are akin to comparative statics about steady states. Whereas Proposition1 shows that a permanent increase in dollar funding has no effects on the LP, the payment volatility does have ef- fects. The results on the long term effects of both shocks also relate to the exorbitant privilege of the dollar. Funding shocks scale the demand for dollar reserves and dollar penalties. Thus, a greater use of the dollar in international funding increases the fiscal revenues. In turn, a greater dollar payment volatility appreciates the value of dollar reserves, offsetting the effect on the US budget constraint. By contrast, if the scale of deposits and reserves
15In Figure3, we consider a version of the model where the only shock is a Markov process for volatility of dollar withdrawals, which is solved fully non-linear, as described in Appendix .
27 is the same in both countries, but dollar funding is more volatile, the US can fund its liabilities at a lower cost. Policy Intervention: Interest Policy. We now study how monetary policy affects the ex- change rate. We start by considering the effect of a change in the nominal policy rates.
Proposition 3 (Effects of Changes in Policy Rates). Consider a temporary change in the dollar interest rate on reserves, i∗,m while holding fixed the policy spread (i∗,w − i∗,m). 1) If the shock is temporary (iid) it appreciates the dollar, raises the liquidity ratio and reduces the premia:
d log e d log µ d log P ∗ R∗,m ∗,m = ∗,m = − ∗,m = b ∗ ∈ (0, 1] and d log (1 + i ) d log (1 + i ) d log (1 + i ) (R − LPµ∗ · µ ) dBP = −Rm (d log (1 + im) − d log e) < 0. 2) If the shock is permanent (random walk), it appreciates the dollar, increases the liquidity ratio and reduces all premia:
d log e d log µ∗ d log P ∗ 1 ∗,m = ∗,m = − ∗,m = − ∗ > 0 and d log (1 + i ) d log (1 + i ) d log (1 + i ) LPµ∗ · µ dBP = dLP = −Rmd log (1 + im).
Proposition3 establishes that in response to an increase in the US nominal rate, the dol- lar appreciates, the liquidity ratio increases and the liquidity premium falls. The apprecia- tion of the dollar follows a standard effect: a higher nominal rate leads to a larger demand for dollars, which in equilibrium requires a dollar appreciation. Absent liquidity premia, the difference in nominal returns across currencies would be exactly offset by the expected depreciation of the dollar, following the current revaluation. With a liquidity premium, the expected depreciation is not one for one: given the larger abundance of dollar re- serves, there is a decrease in the marginal value of dollarreserves together with reduction in dollar liquidity premium. This result breaks the tight connection between interest-rate differentials and expected depreciation, and thus explains the forward-premium (Fama) puzzle. Policy Intervention: Open-market operations. Finally, we consider the effects of open market operations. In the model description, expansions in M are implemented with transfers—helicopter drops. In practice, central banks conduct open-market operations
28 purchasing assets and issuing central bank liabilities. We now modify the model and as- sume that the central bank buys private securities which we denote by St. To do so, we assume that securities are supplied inelastically and that households securities are per- fect substitutes for private deposits.16 Thus, the demand for deposits and securities jointly given by: us d ¯d ς Dt + St = Θt Rt+1 ,
and analogously for dollar securities. We denote the holdings of securities by the central g d g bank as St . The government budget constraint is modified by adding 1 + it St to the sources of funds and St+1 to the uses. We have an analogue equation for the euro. Next, we characterize the effects of an open-market purchase of securities in the US.
Proposition 4 (Effects of Open-Market Operations). Consider an open-market operation in ∗,g ∗ the US starting from a central bank balance sheet where securities St are fraction the Γ of real ∗ ∗,g ∗ ∗ reserves, Pt · St = Γ · Mt . 1) If the shock is temporary (iid) it depreciates the dollar, increases the liquidity ratio and lowers the premia: ∗ ∗ ∗ ∗ d log e d log P LPθ∗ θµ∗ µ (1 − µ ) ∗,g = − ∗,g = b ∗ ∗ ∗ ≤ 0, d log St d log St R − LPθ∗ θµ∗ µ (1 − Γ )
∗ ∗ ∗ b d log µ µ (1 − µ ) R ∗,m ∗ ∗,g = b ∗ ∗ ∗ ∈ [0, 1] , and dBP = dLP = −R d log P ≤ 0. d log St R − (1 − Γ ) LPθ∗ θµ∗ µ
2) If the shock is permanent (random walk), it depreciates the dollar and is neutral on the liquidity ratio and the premia:
d log e d log P ∗ Γ∗ = − = − (1 − µ∗) ≤ 0, d log S∗,G d log S∗,G 1 − Γ∗ and 16In practice, households hold securities indirectly through pension funds, non-financial institutions, etc. For simplicity, we assume that securities and deposits are perfect substitutes for households.
29 (a) Liquidity (b) Real Rates on Reserves
(c) Exchange Rate (e) Deposit Rates
Figure 3: Equilibrium solution for a range of values of volatility
Connecting the theoretical results with the empirical results. Recall from Section2 that there is a positive relationship between the dollar liquidity ratio and the appreciation of the dollar, once controlling for monetary policy. Thus, we are interested in explaining this co-movement through the effects of the unobservable shocks, shocks to the dollar funding and the payment volatility, There is an important difference in the prediction of funding shock and the payment volatility shocks. Whereas funding shocks lead to a reduction in the liquidity ratio, the payment volatility shock leads to an increase in the liquidity ratio. These results suggest that to reconcile the empirical observations, volatility shocks ought to play an important role in driving the exchange rate. The previous results were shown for two extreme scenarios, iid and permanent shocks. In section5, we show that a calibrated version of the model with more general processes
30 for both shocks is indeed consistent with the empirical results. Here, we are interested in theoretically characterizing how, for AR(1) processes different parameters affect the regression coefficients that we obtain in Section2. In particular, we assume that all exoge- nous process for x follow a log AR(1) process of the form:
x x x x ln (xt) = (1 − ρ ) ln (xss) + ρ · ln (xt−1) + Σ εt (26)
where ρx is the mean-reversion rate of x and Σx its volatility. We have the following formal result for the regression coefficient of the exchange rate against the dollar liquidity ratio, e x x βµ∗ given the {ρ , Σ } and different equilibrium objects.
Proposition 5. The regression coefficient of the change in the liquidity against the change in the liquidity ration is the weighted average:
e X βµ∗ = βx · wx x∈{σ∗,D∗}
where βx represents the regression coefficient if only the shock x is activated: