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Risk Parity: in the Spotlight After 50 Years

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Risk Parity: in the Spotlight After 50 Years RISK PARITY: IN THE SPOTLIGHT AFTER 50 YEARS Christopher A. Levell, ASA, CFA, CAIA Partner Introduction can achieve expected returns above the efficient frontier by allowing the portfolio to be levered. Risk Parity is a simple idea: maximize diversifica- tion by taking equal risk in each investment. This Despite the soundness of Tobin’s idea, the use of concept can be used to guide portfolio diversifi- leverage by institutional investors has long been cation, by decreasing assets with large shares of considered taboo. Many investors have a greater the investment risk budget and increasing lower- awareness of the potential dangers of leverage risk assets. In practice, risk parity is used in an than an appreciation of its benefits when pru- increasing number of investment strategies, and dently used. They may dismiss the idea of lever- can even be pursued at the total portfolio level. age out of hand, without assessing its pros and Most risk parity approaches involve leverage, cons. But attitudes are shifting. Investment pro- which has made recent headlines, with reporters questioning the logic behind gearing low risk as- sets to increase return. However, this approach is THIS APPROACH IS ACTUALLY AN actually an insight that is more than 50 years old. INSIGHT THAT IS MORE THAN 50 Harry Markowitz introduced the concept of the YEARS OLD. “efficient frontier” in 1952. Using assumptions for expected return, standard deviation of return, fessionals in particular are increasingly aware of and correlations between assets, the efficient the constraints on portfolio performance imposed frontier is a graphical depiction of the highest ex- by arbitrary restrictions on style, geography, pected return possible for a given level of risk. Bill shorting, and leverage. Tobin and others pointed out in 1958 that the frontier can be improved upon by adding risk-free More open attitudes about moderate leverage investments to the total portfolio. To the left of have led managers to develop products which the frontier, an allocation on the efficient frontier exploit Tobin’s insight. Many of these products (the tangent portfolio) is combined with risk-free come under the name "risk parity." assets (generally cash or Treasuries) to create a Diversification line — dubbed the “capital market line” — that represents portfolios with higher returns for a set Diversification has always been key to successful level of risk than those on the frontier. long-term investing. To measure the benefits of diversification, metrics such as the Sharpe ratio, a The capital market line also extends to the right measure of a portfolio’s excess return per unit of and above the frontier. Tobin showed that lever- risk, were developed. What does a fully diversi- ing a well diversified and low-risk portfolio pro- fied portfolio look like? Using the tools mentioned duces a risk/return trade-off superior to that of above, we would look for the portfolio with the an unlevered traditional portfolio concentrated in highest Sharpe ratio — specifically, the tangent risky assets. Put differently, an investor portfolio in Figure 1. This portfolio has relatively March 2010 low risk; unfortunately, it is also one of the lowest Risk budgeting can be used to calculate the risk returning portfolios on the frontier. allocations of a portfolio by asset class, based on the assumed volatility of each asset class and its Broadly speaking, investors follow two main ave- correlations to other assets. We will examine a nues to boosting returns: taking more beta (or hypothetical asset allocation, first on the usual market) risk along the frontier, and seeking alpha capital basis, and then on a risk basis. Figure 2 is (or manager outperformance). The first technique, an example of a typical risk budget, with a portfo- taking more beta risk, has led to portfolios with lio well diversified across liquid asset classes. equity-heavy mixes that have concerned NEPC for many years. The second technique, pursuing Notice that many of the portfolio’s diversifying alpha, is employed in a huge array of products, asset classes each have a 5% allocation, yet their many of them quite successful, but is more expen- share of the risk budget ranges from 0% sive and fleeting than market beta exposure. (rounded) for several to 9% for emerging market equities. Also, as NEPC has noted frequently, eq- AN ASSET ALLOCATION WITH uity risk dominates the risk budget; in this case, an asset allocation with 55% equities leads to 85% of 55% EQUITIES LEADS TO 85% OF risk. RISK. With this typical risk budget framework, we can construct a portfolio with risk parity — that is, one Yet there is a third way to increase expected risk in which each asset class contributes an equal and return, one that exploits the capital market amount of risk. In essence, we “reverse-engineer” line (CML) defined in the previous section. If in- vesting and borrowing can be done at the risk- Figure 1: Efficient Frontier with Capital Market Line free rate, then this line can be drawn from the risk-free rate, tangent to the efficient fron- tier. Portfolios on the CML are more efficient than port- folios on the efficient frontier (Figure 1); that is, they achieve more return at a given level of risk. But to position a portfo- lio along the CML and in- crease risk and return, lever- age is needed in order to in- vest more than 100% in the tangent portfolio. The Sharpe ratio for all portfolios on the CML is constant; an investor can simply choose the level of risk to be taken. the process, starting with a portfolio of equal risks Risk Parity from each asset class and then deriving the un- derlying capital allocation. Figure 3 reveals the One simple way to diversify is to allocate equal results of this exercise. capital to each asset class. Unfortunately, such an allocation is not efficient, and for that reason has With ten asset classes, each is 10% of the risk been called “naïve diversification." The tangent budget, as shown in the bottom graph. From this portfolio, in contrast, tends to have allocations we derived capital asset allocations as shown in that are equally risk weighted, leading to the term the top graph. Some asset classes, such as core “risk parity.” bonds, gain a greater share of capital due to their 2 Risk Parity: In the Spotlight After 50 Years relatively low volatility. The allocations of other folio can achieve returns significantly above those asset classes, such as commodities, expand be- of portfolios along the efficient frontier. cause of their low correlation to other kinds of assets. Economic Scenario Method This risk parity portfolio has an expected return Before discussing the risks and opportunities of of 5.9%, with a standard deviation of 6.9%, using leverage, we will examine another framework for NEPC’s 2010 assumptions. Regardless of the risk- creating risk parity portfolios. Instead of assessing free rate, this portfolio has a Sharpe ratio that prospective risks, returns, and correlations, this exceeds most institutional funds. Unfortunately, method aims to have investments that perform its expected return is lower than required by well across a variety of economic environments. many programs. This brings us back to the use of The typical economic framework is based on pro- leverage along the Capital Market Line. jections of economic growth and inflation, very similar to those formulated by NEPC. If we lever this portfolio once, for 2:1 leverage, we increase the geometric return to 8.9% and the Specific historical periods can be tied to each of standard deviation to 13.9%. This is an attractive these inflation/growth regimes. For any given pe- risk/return profile that would be acceptable to riod, the performance of individual asset classes most investors, if they could become comfortable has varied widely, in large part due to the diver- with the distinctive risks arising from leverage. gent dynamics of inflation and growth. For exam- This 1x leverage example is presented in Figure 4. ple, the United States and much of the rest of the world experienced unprecedented disinflation Figure 4 reveals the 2010 return and risk assump- and strong economic growth during the 1980s and tions of the ten liquid asset classes used in the 1990s. These forces helped drive extraordinary risk budgets, and the unconstrained efficient fron- returns for traditional stock and bond invest- tier of all combinations of these assets. Actually, ments. In 2000–2002, a “perfect storm” of tum- we should note that the efficient frontier is based bling stock markets and lower interest rates was on all long-only, unlevered combinations of assets. rough on equity markets and raised pension li- The basic risk parity portfolio plots very close to abilities, but was good for bonds. The overexten- the frontier, close to the tangent portfolio in Fig- sion of the 1960s and the stagflation of the 1970s ure 1. Importantly, a risk budget methodology for witnessed high inflation. Traditional stocks and creating the risk parity portfolio does not guaran- bonds fare the worst in times of stagflation, now tee that it will have the maximum Sharpe ratio. considered by many observers as a plausible However, we would expect either methodology to threat for the first time in 30 years. produce very similar results. As leverage in- creases along the line, the levered risk parity port- Figure 2: Typical Asset Allocation with Risk Budget 3 Risk Parity: In the Spotlight After 50 Years From a portfolio construction standpoint, all three Illiquidity: assets that are hard to sell, or that approaches to achieving risk parity — a levered can be sold quickly only with a severe dis- tangency portfolio, an equally apportioned risk count.
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