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PPP May not Hold Afterall: A Further Investigation

  • Serena Ng

    ()

    (Department of Economics, Johns Hopkins University)

  • Pierre Perron

    ()

    (Department of Economics, Boston University)

In a recent paper, Engel, C. (1999) presents monte-carlo evidence to suggest that unit root tests cannot detect a non-stationary component in the real exchange rate even when this component accounts for almost half of its longhorizon forecast error variance. This hidden non-stationary component led to the conclusion that long run purchasing power parity might not hold afterall. In this note, we first point out some conceptual difficulties with the statistic being used to measure the size of the non-stationary component, and then argue that it bears no systematic relationship with rejection rates in unit root tests. The problems stem from near observational equivalence of the simulated model in not one, but two dimensions. We then discuss the steps a practitioner can take to minimize Type I error in cases when the non-stationary component is hard to detect. Real exchange rate data for 19 countries are examined and estimates are obtained for the duration of the real exchange rate shocks.

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Article provided by Society for AEF in its journal Annals of Economics and Finance.

Volume (Year): 3 (2002)
Issue (Month): 1 (May)
Pages: 43-64

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Handle: RePEc:cuf:journl:y:2002:v:3:i:1:p:43-64
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  2. Robert J. Shiller & Pierre Perron, 1985. "Testing the Random Walk Hypothesis: Power versus Frequency of Observation," NBER Technical Working Papers 0045, National Bureau of Economic Research, Inc.
  3. Robert R Tchaidze, 2001. "Estimating Taylor Rules in a Real Time Setting," Economics Working Paper Archive 457, The Johns Hopkins University,Department of Economics.
  4. Serena Ng & Pierre Perron, 2001. "LAG Length Selection and the Construction of Unit Root Tests with Good Size and Power," Econometrica, Econometric Society, vol. 69(6), pages 1519-1554, November.
  5. Ng, Serena & Perron, Pierre, 1997. "Estimation and inference in nearly unbalanced nearly cointegrated systems," Journal of Econometrics, Elsevier, vol. 79(1), pages 53-81, July.
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  7. Robert J. Gordon, 1996. "The Time-Varying NAIRU and its Implications for Economic Policy," NBER Working Papers 5735, National Bureau of Economic Research, Inc.
  8. Campbell, John & Perron, Pierre, 1991. "Pitfalls and Opportunities: What Macroeconomists Should Know about Unit Roots," Scholarly Articles 3374863, Harvard University Department of Economics.
  9. Douglas O. Staiger & James H. Stock & Mark W. Watson, 1997. "How Precise Are Estimates of the Natural Rate of Unemployment?," NBER Chapters, in: Reducing Inflation: Motivation and Strategy, pages 195-246 National Bureau of Economic Research, Inc.
  10. Taylor, John B., 1993. "Discretion versus policy rules in practice," Carnegie-Rochester Conference Series on Public Policy, Elsevier, vol. 39(1), pages 195-214, December.
  11. Engel, C., 1996. "Accounting for U.S. Real Exchange Rate Changes," Discussion Papers in Economics at the University of Washington 96-02, Department of Economics at the University of Washington.
  12. Perron, Pierre & Ng, Serena, 1998. "An Autoregressive Spectral Density Estimator At Frequency Zero For Nonstationarity Tests," Econometric Theory, Cambridge University Press, vol. 14(05), pages 560-603, October.
  13. Perron, P., 1987. "Test Consistency with Varying Sampling Frequency," Cahiers de recherche 8752, Universite de Montreal, Departement de sciences economiques.
  14. Perron, P., 1994. "The Adequacy of Asymptotic Approximations in the Near- Integrated Autoregressive Model with Dependent Errors," Cahiers de recherche 9424, Centre interuniversitaire de recherche en économie quantitative, CIREQ.
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  20. John B. Taylor, 1999. "A Historical Analysis of Monetary Policy Rules," NBER Chapters, in: Monetary Policy Rules, pages 319-348 National Bureau of Economic Research, Inc.
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