We provide a theory of the determination of exchange rates based on capital flows in imperfect financial markets. Capital flows drive exchange rates by altering the balance sheets of financiers that bear the risks resulting from international imbalances in the demand for financial assets. Such alterations to their balance sheets cause financiers to change their required compensation for holding currency risk, thus impacting both the level and volatility of exchange rates. Our theory of exchange rate determination in imperfect financial markets not only rationalizes the empirical disconnect between exchange rates and traditional macroeconomic fundamentals, but also has real consequences for output and risk sharing. Exchange rates are sensitive to imbalances in financial markets and seldom perform the shock absorption role that is central to traditional theoretical macroeconomic analysis. We derive conditions under which heterodox government financial policies, such as currency interventions and taxation of capital flows, can be welfare improving. Our framework is flexible; it accommodates a number of important modeling features within an imperfect financial market model, such as non-tradables, production, money, sticky prices or wages, various forms of international pricing-to-market, and unemployment.

The downside risk CAPM (DR-CAPM) can price the cross section of currency returns. The market-beta differential between high and low interest rate currencies is higher conditional on bad market returns, when the market price of risk is also high, than it is conditional on good market returns. Correctly accounting for this variation is crucial for the empirical performance of the model. The DR-CAPM can jointly explain the cross section of equity, commodity, sovereign bond and currency returns, thus offering a unified risk view of these asset classes. In contrast, popular models that have been developed for a specific asset class fail to jointly price other asset classes. JEL classification: F31, F34, G11, G15Keywords: Carry Trade, Currency Returns, Downside Risk, Exchange Rates, UIP, Conditional risk premia, Cross Section of Equities and Commodities * Haas School of Business, University of California at Berkeley, Berkeley, USA. Corresponding author: lettau@haas.berkeley.edu.† Stern School of Business, New York University, New York, USA. We thank Yoshio Nozawa, Fan Yang, and Adrien Verdelhan for sharing their data, the discussants Harald Hau and Ralph Koijen and seminar participants at UC Berkeley, AEA, EFA, EEA and ESNAW meetings, University of Mannheim, University of Michigan, Black Rock, and University of Chicago Booth Junior Faculty Symposium. Financial support from the Clausen Center and the Coleman Fung Center at UC Berkeley are gratefully acknowledged. Maggiori also thanks the International Economics Section, Department of Economics, Princeton University for hospitality during part of the research process for this paper.Foreign exchange is a potentially risky investment and the debate on whether currency returns can be explained by their association with risk factors remains ongoing. We find that the cross section of currency returns can be explained by a risk model where investors are concerned about downside risk. High yield currencies earn higher excess returns than low yield currencies because their co-movement with aggregate market returns is stronger conditional on bad market returns than it is conditional on good market returns. We find that this feature of the data is characteristic not only of currencies but also of equities, commodities and sovereign bonds, thus providing a unified risk view of these markets.The carry trade in foreign exchange consists of investing in high yield currencies while funding the trade in low yield currencies. This trading strategy has historically yielded positive returns because returns on high yield currencies are higher than returns on low yield currencies. A number of explanations for this cross-sectional dispersion have been advanced in the literature, varying from risk based to behavioral.We provide a risk-based explanation by showing that the downside risk capital asset pricing model (DR-CAPM) prices the cross section of currency returns. We follow Ang, Chen, and Xing (2006), who study equity markets, by allowing both the market price of risk and the beta...