For about three decades until the Global Financial Crisis (GFC), Covered Interest Parity (CIP) appeared to hold quite closely—even as a broad macroeconomic relationship applying to daily or weekly data. Not only have CIP deviations significantly increased since the GFC, but potential macrofinancial drivers of the variation in CIP deviations have also become significant. The variation in CIP deviations seems to be associated with multiple factors, not only regulatory changes. Most of these do not display a uniform importance across currency pairs and time, and some are associated with possible temporary considerations (such as asynchronous monetary policy cycles).

Ex-post deviations from uncovered interest parity (UIP) – realized differences between dollar returns on identical assets of different currencies – equal the real interest differential plus real exchange rate growth. Among industrialized countries, UIP deviations are largely explained by unanticipated real exchange rate growth, but among developing countries, real interest differentials are “where the action is.” This observation is due to the greater variability of inflation in developing countries, but may also stem from higher and more variable risks and capital controls in these countries. Also, among developing countries with moderate inflation, offsetting comovements of real interest differentials and real exchange growth support the sticky-price hypothesis.

We provide empirical evidence that deviations from uncovered interest rate parity (UIP) display significant nonlinearities, consistent with theories based on transaction costs or limits to speculation. This evidence suggests that the forward bias documented in the literature may be less indicative of major market inefficiencies than previously thought. Monte Carlo experiments allow us to reconcile these results with the large empirical literature on the forward bias puzzle since we show that, if the true process of UIP deviations were of the nonlinear form we consider, estimation of conventional spot-forward regressions would generate the anomalies documented in previous research.

Asian countries have high demand for U.S. dollars and are sensitive to U.S. dollar funding costs. An important, but often overlooked, component of these costs is the basis spread in the cross-currency swap market that emerges when there are deviations from covered interest parity (CIP). CIP deviations mean that investors need to pay a premium to borrow U.S. dollars or other currencies on a hedged basis via cross-currency swap markets. These deviations can be explained by regulatory changes since the global financial crisis, which have limited arbitrage opportunities and country-specific factors that contribute to a mismatch in the demand and supply of U.S. dollars. We find that an increase in the basis spread tightens financial conditions in net debtor countries, while easing financial conditions in net creditor countries. The main reason is that net debtor countries are, in general, unable to substitute smoothly to other domestic funding channels. Policies that promote reliable alternative funding sources, such as long-term corporate bond market or stable long-term investors, including a “hedging counterpart of last resort,” can help stabilize financial intermediation when U.S. dollar funding markets come under stress.

This note provides an overview of the uncovered interest parity assumption. It traces the history of the interest parity concept, summarizes evidence on the empirical validity of uncovered interest parity, and discusses the implications for macroeconomic analysis. The uncovered interest parity assumption has been an important building block in multiperiod and continuous time models of open economies, and although its validity is strongly challenged by the empirical evidence, its retention in macroeconomic models is supported on pragmatic grounds, at least for the time being, by the lack of much empirical support for existing models of the exchange risk premium.