Uncovered interest parity: The long and the short of it

Uncovered interest rate parity (UIP) is a theoretical relation linking changes in exchange rates and corresponding interest rate differentials. Despite its considerable intellectual appeal, uncovered interest rate parity has very often been found wanting empirically. I reinvestigate this relation using a 17-country panel of historical time series data at its longest—for the US–UK country pair—spanning 217 years. I find results that are largely consistent with theory: over the long term, in most countries, bond yields expressed in common currency bear a positive relationship to one another as UIP predicts. This is in contrast to the very nearly opposite findings reported in much of the literature and now taken as a stylized fact.     

Differential risk premiums and the UIP puzzle

We respecify the uncovered interest rate parity (UIP) conditions by inverting the market price of the risk (Sharpe ratio) formula. Our empirical model provides new insight indicating that violations to the UIP stem from the existence of a risk premium in the exchange rates and from observed market return differentials being a noisy statistic of the markets’ expected return differentials in our respecified model. Using an integrated macro‐micro structure framework for expected market return differentials improves our model fit and the validity of UIP.     

Uncovered Interest Parity,Forward Guidance and the Exchange Rate

Under uncovered interest parity (UIP), the size of the effect on the real exchange rate of an anticipated change in real interest rate differentials is invariant to the horizon at which the change is expected. Empirical evidence using U.S., euro area and UK data points to a substantial deviation from that invariance prediction: expectations of interest rate differentials in the near (distant) future are shown to have much larger (smaller) effects on the real exchange rate than is implied by UIP. Some possible explanations are discussed.     

Co-integrating currencies and yield differentials

This study investigates the relationship between currencies and interest rates of different maturity horizons. The real exchange rate is found to depend both on short-term real domestic and foreign interest rate difference and on long-term real domestic and foreign interest rate difference. Co-integrating regressions of contemporaneous currency rates generate negative and significant coefficients for long-term rate differentials, consistent with uncovered interest parity. Therefore, the expectations hypothesis holds for long horizons. On the other hand, positive coefficients for real short-term interest rate differentials reveal the forward premium puzzle: the failure of uncovered interest parity for short-horizons. Results are partly driven by the very different risk characteristics of short-term bonds and foreign bonds.     

Real interest parity: Evidence from trade partnerships

This study investigates real interest parity (RIP) in trade partnerships, and whether RIP depends on the type of trade partnership, using short term interest rates and the Consumer Price Index (CPI) obtained from the Organization for Economic Cooperation and Development (OECD) database between 1975 and 2016. The investigation employs unit root and stationarity tests on interest rate differentials to study RIP between countries using Germany, United States, and Japan as base countries for selected countries in the European Union (EU), member countries of the North American Free Trade Agreement (NAFTA) and selected Asian countries respectively. The results show evidence in favor of RIP in the selected EU countries. The interest rate differentials of Belgium, France, Italy, Spain and the UK with respect to Germany confirms a long‐run relationship and real interest rate parity. There is also evidence to support the RIP in the other trade partnerships. With the exception of Mexico, the interest rate differentials for all the countries are stationary, and each quickly reverts to its mean.     

Uncovered interest-rate parity over the past two centuries

We study the validity of uncovered interest-rate parity by constructing ultra-long time series that span two centuries. The forward-premium regressions yield positive slope estimates over the whole sample. The estimates become negative only when the sample is dominated by the period of 1980s. We also find that large interest-rate differentials have significantly stronger forecasting powers for currency movements than small interest-rate differentials. Furthermore, when we regress domestic currency returns on foreign bonds against returns on domestic bonds as an alternative test of the parity condition, the null hypotheses of zero intercept and unit slope cannot be rejected in most cases. These results are consistent with a world in which expectations formation is highly imperfect and characterized on the one hand by slow adjustment of expectations to actual regime changes and on the other by anticipations for extended periods of regime changes or other big events that never materialize. An historical account of expected and realized regime changes adds credence to this explanation and illustrates how uncovered interest-rate parity holds over the very long haul but nevertheless can be deviated from over long periods of time due to ex post-expectation errors.     

Are Real Interest Rates Equal Across Countries? An Empirical Investigation of International Parity Conditions

This paper conducts empirical tests of the equality of real interest rates across countries. The empirical evidence strongly rejects the hypothesis of real rate equality and the joint hypotheses of uncovered interest parity and ex ante relative PPP, or the unbiasedness of forward rate forecasts and ex ante relative PPP. The evidence suggests that it is worth studying open economy macroeconomic models which allow: 1) domestic real rates to differ from world rates, 2) time varying risk premiums in the forward market, or 3) deviations from ex ante relative PPP.     

Uncovered interest parity, monetary policy and time-varying risk premia

In a recent paper, McCallum argued that monetary-policy behavior can be responsible for the apparent empirical failure of uncovered interest parity (UIP). The present paper investigates whether optimizing policy behavior can account for the observed regime-dependence of UIP evidence. The main result is that the tradeoff between interest-rate and exchange-rate stability is a potential candidate for the explanation of the apparent failure of UIP and that the consideration of policy reactions can explain why deviations from UIP differ systematically by the exchange-rate regime.     

A Habit-Based Explanation of the Exchange Rate Risk Premium

This paper presents a model that reproduces the uncovered interest rate parity puzzle. Investors have preferences with external habits. Countercyclical risk premia and procyclical real interest rates arise endogenously. During bad times at home, when domestic consumption is close to the habit level, the representative investor is very risk averse. When the domestic investor is more risk averse than her foreign counterpart, the exchange rate is closely tied to domestic consumption growth shocks. The domestic investor therefore expects a positive currency excess return. Because interest rates are low in bad times, expected currency excess returns increase with interest rate differentials.     

Expectations of Exchange Rates and Differential Inflation Rates: Further Evidence on Purchasing Power Parity in Efficient Markets

The paper tests the null hypothesis of ex ante purchasing power parity. The empirical evidence obtained is inconsistent with the null for major industrialized countries over the current floating exchange rate regime. Expected nominal exchange rate changes appear to deviate systematically from expected inflation rate differentials over the same holding period even though real exchange rate changes appear to be serially uncorrelated. This supports the presence of time-varying risk premia in foreign exchange markets and real determinants of exchange rate movements as suggested by equilibrium theories of international asset markets.     

A sentiment-based explanation of the forward premium puzzle

A sentiment-based model of the exchange rate is proposed to understand the forward premium puzzle. Agents over- or under-estimate the growth rate of the economy. All else equal, when perceived domestic growth is higher than perceived foreign growth, the domestic interest rate is higher than the foreign interest rate. At the same time, an econometrician would expect an increase in the home currency value. Together, the model with investor misperception can account for the forward premium puzzle. In addition, misperception helps lower the correlation between consumption growth differentials and exchange rate growth. Finally, this paper provides empirical evidence supporting the mechanism in the sentiment-based explanation.     

Currency futures-spot basis and risk premium

This paper explores the usefulness of currency futures-spot basis in predicting spot rate changes and currency futures returns. We conjecture that the currency risk premium may be an important component of the basis for long-maturity futures contracts, but may not be so for short-maturities. Thus, the basis of long-maturity contracts cannot predict the spot rate changes between now and maturity, rejecting uncovered interest rate parity (UIP), but can predict currency futures returns, which are solely determined by the risk premium. Conversely, the basis of the short-maturity contracts can predict the spot rate changes between now and maturity, validating the UIP, but cannot predict currency futures returns. Empirical tests support these conjectures for the Japanese, British, Swiss, and German currencies over the last two decades. The results are also consistent with Longstaff [Longstaff, F., 2000. The term structure of very short-term rates: new evidence for the Expectation Hypothesis. Journal of Financial Economics 58, 397–415], who shows that the Expectations Hypothesis holds at the very short end of the term structure of interest rates.     

The profitability of carry trades

The uncovered interest parity (UIP) condition suggests that carry trades whereby investors borrow in the low interest rate currency and invest in the high interest rate currency should not result in excess profits over the long run. In this paper, we test the significance of the conventional empirical failure of UIP condition. Using the four bilateral pound parities we fail to detect significant excess carry trade profits for the yen, euro and swiss franc–pound parities. The only parity for which the carry trade consistently makes excess profits is the dollar–pound parity. This result is somewhat surprising as this is the currency pair with the lowest interest rate differential. We are extremely grateful for the anonymous referee’s comments on this paper.     

A Liquidity-Based Resolution of the Uncovered Interest Parity Puzzle

A new monetary theory is set out to resolve the “uncovered interest parity (UIP)” puzzle. It explores the possibility that liquidity properties of money and nominal bonds can account for the puzzle. A key concept in our model is that nominal bonds carry liquidity premia. We show that the UIP can fail to hold under the economic environment where collateral pledgeability and/or liquidity of nominal bonds and/or collateralized credit-based transactions are relatively bigger. Our liquidity-based theory can help understanding many empirical observations that risk-based explanations find difficult to reconcile with.     

The risk adjusted uncovered equity parity

This paper explores the risk adjusted uncovered equity parity model to investigate a degree of market integration for four Asian emerging markets relative to the U.S., Japan and the U.K. from January 1994 to July 2008. The uncovered equity parity is revised to take into account of market risk in a framework of a portfolio rebalancing model. Evidence was found to strongly support our hypotheses; Market risk is significant in international capital flows between the Asian emerging markets and the developed economies, and it can help explain the failure of a traditional uncovered equity (or interest) parity model. The relationship between returns and an appreciation of the exchange rate are divided between the Asian emerging markets and the developed economies, depending on the direction of capital flows.     

Regime switches in exchange rate volatility and uncovered interest parity

We use a regime-switching model to examine how exchange rate volatility is related to the failure of uncovered interest parity. Main findings are as follows. First, exchange rate returns are strongly influenced by regime switches in the relationship between the returns and interest rate differentials. Second, low-yielding currencies appreciate less frequently, but once it occurs, their movements are faster than when they depreciate. Third, depreciation of low-yielding currencies and low volatility are mutually dependent on each other. Finally, these three findings are more evident for shorter horizons. The second and third results are consistent with a market participants’ view: short-term carry trades in a low-volatility environment and their rapid unwinding substantially influence exchange rates. We consider the effects of funding liquidity to explain these results.     

Further Evidence on the Real Interest Rate Parity Hypothesis in Central and East European Countries: Unit Roots and Nonlinearities

This paper analyzes the empirical fulfillment of the real interest rate parity (RIRP) theory for a pool of central and east European countries. To do so, we apply the recently developed Ng and Perron (2001) unit root tests, which are corrected versions of existing unit root tests, and the Kapetanios et al. (2003) unit root test, which generalizes the alternative hypothesis to the globally stationary smooth transition autoregression model. We find evidence in favor of the empirical fulfillment of RIRP, particularly when taking into account the possibility of nonlinearities in the real interest rate differential.     

Taylor rule deviations and out-of-sample exchange rate predictability

The Taylor rule has become the dominant model for academic evaluation of out-of-sample exchange rate predictability. Two versions of the Taylor rule model are the Taylor rule fundamentals model, where the variables that enter the Taylor rule are used to forecast exchange rate changes, and the Taylor rule differentials model, where a Taylor rule with postulated coefficients is used in the forecasting regression. We use data from 1973 to 2014 to evaluate short-run out-of-sample predictability for eight exchange rates vis-à-vis the U.S. dollar, and find strong evidence in favor of the Taylor rule fundamentals model alternative against the random walk null. The evidence of predictability is weaker with the Taylor rule differentials model, and still weaker with the traditional interest rate differential, purchasing power parity, and monetary models. The evidence of predictability for the fundamentals model is not related to deviations from the original Taylor rule for the U.S., but is related to deviations from a modified Taylor rule for the U.S. with a higher coefficient on the output gap. The evidence of predictability is also unrelated to deviations from Taylor rules for the foreign countries and adherence to the Taylor principle for the U.S.     

Monetary policy and inferential expectations of exchange rates

We present a macroeconomic market experiment to isolate the impact of monetary shocks on the exchange rate, as an alternative to SVAR identification. In a non-stochastic treatment, covered interest rate parity holds and predicted exchange rates are tracked well. In a stochastic treatment, we model expectations using a Neyman–Pearson hypothesis test (inferential expectations) and find evidence of belief conservatism and uncovered interest rate parity failure. The market environment magnifies belief conservatism, which is opposite to the standard claim that markets tend to eliminate individual choice anomalies.     

Purchasing power,interest rate parities and the modified Fisher effect in presence of tax agreements

This paper shows that in a world with different rates of inflation and taxation, in the presence of an international tax agreement, the simultaneous coexistence of the purchasing power parity mechanism, the interest rate parity mechanism, and the revised Fisher effect is impossible. The analysis reveals a possible inherent instability of interest rates and exchange rates generated by inflation. This instability is greater the larger the tax rate differentials among countries.