Yangru Wu

Are Real Exchange Rates Nonstationary? Evidence from a Panel-Data Test

It is well documented that real exchange rates between the United States and many industrialized countries in the post-Bretton Woods period are integrated. This result implies that purchasing power parity (PPP) does not hold even as a long run relationship. This paper demonstrates that the failure to reject the unit-root hypothesis may result from the low power of existing univariate test procedures. I test for unit roots in real exchange rates by employing a more powerful panel-based procedure. Using both CPI and WPI real dollar exchange rate data, I strongly reject the null hypothesis of a unit root. My results provide overwhelming support for the long-run PPP under the current float. Copyright 1996 by Ohio State University Press.

EXPLOSIVE BEHAVIOR IN THE 1990s NASDAQ: WHEN DID EXUBERANCE ESCALATE ASSET VALUES?

A recursive test procedure is suggested that provides a mechanism for testing explosive behavior, date-stamping the origination and collapse of economic exuberance, and providing valid confidence intervals for explosive growth rates. The method involves the recursive implementation of a right-side unit root test and a sup test, both of which are easy to use in practical applications, and some new limit theory for mildly explosive processes. The test procedure is shown to have discriminatory power in detecting periodically collapsing bubbles, thereby overcoming a weakness in earlier applications of unit root tests for economic bubbles. Some asymptotic properties of the Evans (1991) model of periodically collapsing bubbles are analyzed and the paper develops a new model in which bubble duration depends on the strength of the cognitive bias underlying herd behavior in the market. The paper also explores alternative propagating mechanisms for explosive behavior based on economic fundamentals under time varying discount rates. An empirical application to the Nasdaq stock price index in the 1990s provides confirmation of explosiveness and date-stamps the origination of financial exuberance to June 1995, prior to the famous remark in December 1996 by Alan Greenspan about irrational exuberance in financial markets, thereby giving the remark empirical content.

Mean Reversion across National Stock Markets and Parametric Contrarian Investment Strategies

For U.S. stock prices, evidence of mean reversion over long horizons is mixed, possibly due to lack of a reliable long time series. Using additional cross-sectional power gained from national stock index data of 18 countries during the period 1969 to 1996, we find strong evidence of mean reversion in relative stock index prices. Our findings imply a significantly positive speed of reversion with a half-life of three to three and one-half years. This result is robust to alternative specifications and data. Parametric contrarian investment strategies that fully exploit mean reversion across national indexes outperform buy-and-hold and standard contrarian strategies. Copyright The American Finance Association 2000.

Random walk versus breaking trend in stock prices: Evidence from emerging markets

This paper investigates whether stock-price indexes of seventeen emerging markets can be characterized as random walk (unit root) or mean reversion processes. We implement a test that can account for structural breaks in the underlying series and is more powerful than standard tests. We find that for fourteen countries, stock prices exhibit structural breaks. Furthermore, for ten countries, the null hypothesis of a random walk can be rejected at the one or 5% significance level. Our results indicate that ignoring structural breaks that arise from the liberalization of emerging markets can lead to incorrect inference that these indices are characterized by random walks, and are consistent with the points made by Bekaert et al. [J. Int. Money Finan. 21 (2002) 295]. Our findings hold true regardless of whether stock indexes are denominated in US dollar terms, in local currencies terms, or in real terms. 2002 Elsevier Science B.V. All rights reserved.

UNDERSTANDING SPOT AND FORWARD EXCHANGE RATE REGRESSIONS

Using the Kalman filter, we obtain maximum likelihood estimates of a permanent-transitory components model for log spot and forward dollar prices of the pound, the franc, and the yen. This simple parametric model is useful in understanding why the forward rate may be an unbiased predictor of the future spot rate even though an increase in the forward premium predicts a dollar appreciation. Our estimates of the expected excess return on short-term dollar-denominated assets are persistent and reasonable in magnitude. They also exhibit sign fluctuations and negative covariance with the estimated expected depreciation.

Hysteresis in Unemployment: Evidence from OECD Countries

Existing studies using standard unit-root tests generally cannot reject the null hypothesis of a unit root in unemployment rates. These findings have been interpreted as support for the hysteresis hypothesis. In this paper, we analyze a panel of unemployment rates of fifteen OECD countries by using a panel-based test. The test exploits the cross-section variations of the constituent series and is more powerful. The critical values are simulated based on our specific panel sizes and time periods. It is found that the null hypothesis of a unit root in unemployment rates can be rejected in general. This casts some doubt on the hysteresis hypothesis and provides limited support for the natural-rate hypothesis of unemployment for these countries.

Nonlinear prediction of exchange rates with monetary fundamentals

Abstract This paper employs a neural network (NN) to study the nonlinear predictability of exchange rates for four currencies at the 1-, 6- and 12-month forecast horizons. We find that our neural network model with market fundamentals cannot beat the random walk (RW) in out-of-sample forecast accuracy, although it occasionally shows a limited market-timing ability. The neural network model without monetary fundamentals forecasts somewhat better for the British pound and the Canadian dollar. The model also exhibits some market-timing ability for the Deutsche mark at the 6- and 12-month horizons, and for the Canadian dollar at the 1-month horizon. In general, the model performs more poorly when it becomes more complex or when the forecast horizon lengthens. Our overall results are more on the negative side and suggest that neither nonlinearity nor market fundamentals appear to be very important in improving exchange rate forecast for the chosen horizons.

Mean Reversion in Interest Rates: New Evidence from a Panel of OECD Countries

Previous studies show that the standard univariate unit root tests cannot reject the hypothesis that interest rates follow integrated processes. In this paper, the authors pool interest rate data of twelve OECD countries and implement a multivariate test. It is found that the unit root hypothesis can be decisively rejected. Copyright 1996 by Ohio State University Press.

Mean reversion in stock prices: evidence from emerging markets

This paper investigates whether stock‐price indexes of emerging markets can be characterized as random walk (unit root) or mean reversion processes. We implement a panelbased test that exploits cross‐sectional information from seventeen emerging equity markets during the period January 1985 to April 2002. The gain in power allows us to reject the null hypothesis of random walk in favor of mean reversion at the 5 percent significance level. We find a positive speed of reversion with a half‐life of about 30 months. These results are similar to those documented for developed markets. Our findings provide an interesting comparison to existing studies on more matured markets and reduce the likelihood of earlier mean reversion findings as attributable to data mining.

Explaining Exchange Rate Risk in World Stock Markets: A Panel Approach

Using a GARCH approach, we estimate a time-varying two-factor international asset pricing model for weekly equity index returns of 16 OECD countries. A trade-weighted basket of exchange rates and the MSCI world market index are used as risk factors. We find significant currency risk exposures in country equity index returns. We then explain these currency betas using several country-specific macroeconomic variables with a panel approach. We find that imports, exports, credit ratings, and tax revenues significantly affect currency risks in a way that is consistent with some economic hypotheses. Similar conclusions are obtained by using lagged explanatory variables, and thus these macroeconomic variables may be useful as predictors of currency risk exposures. Our results are robust to a number of alternative specifications.