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State of the Art Unit Root Tests and the PPP Puzzle

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Author Info
Claude Lopez (University of Cincinnati)
Christian J. Murray (University of Houston)
David H. Papell (University of Houston)

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Abstract

Using median-unbiased estimation, recent research has questioned the validity of Rogoff’s “remarkable consensus” of 3-5 year half-lives of deviations from PPP. These estimates, however, are based on unit root tests with low power. We extend median-unbiased estimation to the efficient unit root test of Elliott, Rothenberg, and Stock (1996). We find that median-unbiased estimation based on the more powerful unit root test has the potential to tighten confidence intervals for 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 above 3 years. Thus, while previous confidence intervals for half-lives are consistent with virtually anything, our tighter confidence intervals now rule out economic models with nominal rigidities as candidates for explaining the observed behavior of real exchange rates. Therefore, while we obtain more information using efficient unit root tests on longer term data, this information moves us away from solving the PPP puzzle.

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Paper provided by EconWPA in its series Macroeconomics with number 0310009.

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Length: 27 pages
Date of creation: 08 Oct 2003
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Handle: RePEc:wpa:wuwpma:0310009

Note: Type of Document - Acrobat PDF; prepared on PC; to print on A4; pages: 27 ; figures: included
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Related research
Keywords: PPP Unit root test Median-unbiased DF-GLS test;

Find related papers by JEL classification:
F3 - International Economics - - International Finance
C22 - Mathematical and Quantitative Methods - - Single Equation Models; Single Variables - - - Time-Series Models; Dynamic Quantile Regressions

This paper has been announced in the following NEP Reports:

References listed on IDEAS
Please report citation or reference errors to , or , if you are the registered author of the cited work, log in to your RePEc Author Service profile, click on "citations" and make appropriate adjustments.:
  1. Cheung, Yin-Wong & Lai, Kon S., 2000. "On the purchasing power parity puzzle," Journal of International Economics, Elsevier, vol. 52(2), pages 321-330, December. [Downloadable!] (restricted)
  2. Lutz Kilian, 1998. "Small-Sample Confidence Intervals For Impulse Response Functions," The Review of Economics and Statistics, MIT Press, vol. 80(2), pages 218-230, May. [Downloadable!] (restricted)
  3. Diebold, Francis X & Husted, Steven & Rush, Mark, 1991. "Real Exchange Rates under the Gold Standard," Journal of Political Economy, University of Chicago Press, vol. 99(6), pages 1252-71, December. [Downloadable!] (restricted)
    Other versions:
  4. Rossi, Barbara, 2002. "Confidence Intervals for Half-life Deviations from Purchasing Power Parity," Working Papers 02-08, Duke University, Department of Economics. [Downloadable!]
    Other versions:
  5. West, Kenneth D., 1987. "A note on the power of least squares tests for a unit root," Economics Letters, Elsevier, vol. 24(3), pages 249-252. [Downloadable!] (restricted)
  6. Abuaf, Niso & Jorion, Philippe, 1990. " Purchasing Power Parity in the Long Run," Journal of Finance, American Finance Association, vol. 45(1), pages 157-74, March. [Downloadable!] (restricted)
  7. Kenneth Rogoff, 1996. "The Purchasing Power Parity Puzzle," Journal of Economic Literature, American Economic Association, vol. 34(2), pages 647-668, June. [Downloadable!] (restricted)
  8. Bruce E. Hansen, 1999. "The Grid Bootstrap And The Autoregressive Model," The Review of Economics and Statistics, MIT Press, vol. 81(4), pages 594-607, November. [Downloadable!] (restricted)
  9. Elliott, Graham & Rothenberg, Thomas J & Stock, James H, 1996. "Efficient Tests for an Autoregressive Unit Root," Econometrica, Econometric Society, vol. 64(4), pages 813-36, July. [Downloadable!] (restricted)
    Other versions:
  10. 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. [Downloadable!] (restricted)
    Other versions:
  11. Atsushi Inoue & Lutz Kilian, 2002. "Bootstrapping Autoregressive Processes with Possible Unit Roots," Econometrica, Econometric Society, vol. 70(1), pages 377-391, January. [Downloadable!] (restricted)
    Other versions:
  12. Engel, Charles, 2000. "Long-run PPP may not hold after all," Journal of International Economics, Elsevier, vol. 51(2), pages 243-273, August. [Downloadable!] (restricted)
    Other versions:
  13. Cheung, Yin-Wong & Lai, Kon S., 1994. "Mean reversion in real exchange rates," Economics Letters, Elsevier, vol. 46(3), pages 251-256, November. [Downloadable!] (restricted)
  14. Murray, Christian J. & Papell, David H., 2002. "The purchasing power parity persistence paradigm," Journal of International Economics, Elsevier, vol. 56(1), pages 1-19, January. [Downloadable!] (restricted)
    Other versions:
  15. Andrews, Donald W K, 1993. "Exactly Median-Unbiased Estimation of First Order Autoregressive/Unit Root Models," Econometrica, Econometric Society, vol. 61(1), pages 139-65, January. [Downloadable!] (restricted)
  16. Alan M. Taylor, 2000. "A Century of Purchasing-Power Parity," NBER Working Papers 8012, National Bureau of Economic Research, Inc. [Downloadable!] (restricted)
    Other versions:
  17. Glen, Jack D., 1992. "Real exchange rates in the short, medium, and long run," Journal of International Economics, Elsevier, vol. 33(1-2), pages 147-166, August. [Downloadable!] (restricted)
  18. Andrews, Donald W K & Chen, Hong-Yuan, 1994. "Approximately Median-Unbiased Estimation of Autoregressive Models," Journal of Business & Economic Statistics, American Statistical Association, vol. 12(2), pages 187-204, April.
  19. Lutz Kilian & Tao Zha, 2002. "Quantifying the uncertainty about the half-life of deviations from PPP," Journal of Applied Econometrics, John Wiley & Sons, Ltd., vol. 17(2), pages 107-125. [Downloadable!]
  20. Lutz Kilian, 1999. "FINITE-SAMPLE PROPERTIES OF PERCENTILE AND PERCENTILE-t BOOTSTRAP CONFIDENCE INTERVALS FOR IMPULSE RESPONSES," The Review of Economics and Statistics, MIT Press, vol. 81(4), pages 652-660, November. [Downloadable!] (restricted)
  21. Hall, Alastair R, 1994. "Testing for a Unit Root in Time Series with Pretest Data-Based Model Selection," Journal of Business & Economic Statistics, American Statistical Association, vol. 12(4), pages 461-70, October.
  22. Lothian, James R & Taylor, Mark P, 1996. "Real Exchange Rate Behavior: The Recent Float from the Perspective of the Past Two Centuries," Journal of Political Economy, University of Chicago Press, vol. 104(3), pages 488-509, June. [Downloadable!] (restricted)
Full references

Cited by:
(explanations, Please report citation or reference errors to , or , if you are the registered author of the cited work, log in to your RePEc Author Service profile, click on "citations" and make appropriate adjustments.)

  1. Caporale, Guglielmo Maria & Cerrato, Mario, 2004. "Panel Data Tests of PPP. A Critical Overview," Economics Series 159, Institute for Advanced Studies. [Downloadable!]
    Other versions:
  2. Claude Lopez, 2003. "An Improved Panel Unit Root Test Using GLS-Detrending," Econometrics 0310006, EconWPA, revised 24 Oct 2003. [Downloadable!]
    Other versions:
  3. Sofiane H. Sekioua, 2004. "Real interest parity (RIP) over the 20th century: New evidence based on confidence intervals for the dominant root and half-lives of shocks," Money Macro and Finance (MMF) Research Group Conference 2004 91, Money Macro and Finance Research Group. [Downloadable!]
  4. Ruxandra Prodan, 2004. "Potential Pitfalls in Determining Multiple Structural Changes with an Application to Purchasing Power Parity," Econometric Society 2004 North American Summer Meetings 90, Econometric Society. [Downloadable!]
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