Research - Exchange Rates

Median-Unbiased Estimation in DF-GLS Regressions and the PPP Puzzle

with Murray C.J., and D.H. Papell, Applied Economics, 45(4), 455-464, 2013.      Using median-unbiased estimation based on Augmented-Dickey-Fuller (ADF) regressions, recent research has questioned the validity of Rogoff’s “remarkable consensus” of 3-5 year half-lives of deviations from PPP. The confidence intervals of these half-life estimates, however, are extremely wide, with lower bounds of about one year and upper bounds of infinity. We extend median-unbiased estimation to the DF-GLS regression of Elliott, Rothenberg, and Stock (1996). We find that combining median-unbiased estimation with this regression has the potential to tighten confidence intervals for the half-lives. Using long horizon real exchange rate data, we find that the typical lower bound of the confidence intervals for median-unbiased half-lives is just under 3 years. Thus, while previous confidence intervals for median-unbiased half-lives are consistent with virtually anything, our tighter confidence intervals are inconsistent with economic models with nominal rigidities as candidates for explaining the observed behavior of real exchange rates and move us away from solving the PPP puzzle.

Evidence of Purchasing Power Parity for the Floating Regime Period

with D.H. Papell, Journal of International Money and Finance, 27(1),156-164 13, 2007.      This paper investigates the PPP hypothesis within industrialized countries for the post-Bretton Woods period via two panel unit root tests, the DF–GLS–SUR and the ADF–SUR tests, respectively developed by Lopez [A panel unit root with good power in small samples. Econometric Reviews, 2009] and Levin et al. [2002. Unit root tests in panel data: asymptotic and finite-sample properties. Journal of Econometrics 108 (1), 1–24]. Both approaches allow for data specific serial and contemporaneous correlation. While both tests provide PPP evidence for the post-1973 period, the more powerful DF–GLS–SUR test demonstrates consistently stronger results, especially for the 1973–1998 period.

Convergence to Purchasing Power Parity at the Commencement of the Euro

with D.H. Papell, Review of International Economics, 15(1), 1–16, 2007.      We investigate convergence towards Purchasing Power Parity (PPP) within the Euro Zone and between the Euro Zone and its main partners using panel data methods. We find strong rejections of the unit root hypothesis, and therefore evidence of PPP, in the Euro Zone for different numeraire currencies, as well as in the Euro Zone plus the United States with the dollar as the numeraire currency, starting between 1996 and 1999. The process of convergence towards PPP, however, begins earlier, following the currency crises of 1992 and 1993, adoption of the Maastricht Treaty, and official completion of the Single Market.

State of the Art Unit Root Tests and Purchasing Power Parity

With C.J. Murray and D.H. Papell, Journal of Money Credit and Banking, 37,361-369, 2005. Although the question of whether Purchasing Power Parity (PPP) holds in the long run has been extensively studied, the answer is still controversial. Some of the strongest evidence is provided by Taylor (2002), who concludes that long-run PPP held over the twentieth century. We argue that this conclusion is quite sensitive to the use of suboptimal lag selection in unit root tests. Using superior lag selection methods, we find that long run PPP held for the real exchange rates of only 9 out of the 16 industrialized countries in Taylor’s sample with the U.S. dollar as the base currency.