Currency Wars, Trade Wars, and Global Demand Olivier Jeanne Johns Hopkins University∗ January 2021 Abstract This paper presents a tractable model of a global economy in which national social planners can use a broad range of policy instruments|the nominal interest rate, taxes on imports and exports, taxes on capital flows or foreign exchange interventions. Low demand may lead to unemployment because of downward nominal wage stickiness. Markov perfect equilibria with and without international cooperation are characterized in closed form. The welfare costs of trade and currency wars crucially depend on the state of global demand and on the policy instruments that are used by national social planners. National social planners have more incentives to deviate from free trade when global demand is low. ∗Olivier Jeanne: Department of Economics, Johns Hopkins University, 3400 N.Charles Street, Baltimore MD 21218; email:
[email protected]. I thank seminar participants, especially Alberto Martin, Emmanuel Farhi, Charles Engel, Dmitry Mukhin and Oleg Itskhoki, at the NBER Con- ference on Capital Flows, Currency Wars and Monetary Policy (April 2018), the 2019 ASSA meeting, the Board of the US Federal Reserve System, the University of Maryland, the Uni- versity of Virginia, Georgia State University, the University of Southern California, the Federal Reserve of New York, the University of Wisconsin and the Graduate Institute in Geneva for their comments. 1 1 Introduction Countries have regularly accused each other of being aggressors in a currency war since the global financial crisis. Guido Mantega, Brazil's finance minister, in 2010 blamed the US for launching a currency war through quantitative easing and a lower dollar.1 At the time Brazil itself was trying to hold its currency down by accumulating reserves and by imposing a tax on capital inflows.