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The Power of the "Objective" Bayesian Unit-Root Test


  • Francis W. Ahking

    (University of Connecticut)


Some researchers, for example, Koop (1992), and Sims (1988), advocated for Bayesian alternatives to unit-root testing over the classical approach using the augmented Dickey-Fuller test (ADF). This paper studies the power of what Koop (1992) has called the "Objective" Bayesian approach to unit-root testing. Koop's "objective" Bayesian test is interesting in light of the call by Phillips (1991a, 1991b) for more objective Bayesian analysis of time series. We apply the "objective" Bayesian unit-root test to a study of long-run purchasing power parity (PPP) in the post-Bretton Woods era and also Monte Carlo simulations. Overall, our results suggest that the "objective" Bayesian test is biased in favor of trend-stationarity. We conclude that, at least for the "objective" Bayesian test, it is not better than the classical ADF approach in unit-root tests, and because of its bias, the "objective" priors suggested by Koop is not appropriate.

Suggested Citation

  • Francis W. Ahking, 2004. "The Power of the "Objective" Bayesian Unit-Root Test," Working papers 2004-14, University of Connecticut, Department of Economics.
  • Handle: RePEc:uct:uconnp:2004-14 Note: I wish to thank Professor Stephen M. Miller, participants at the Southern Economic Association Annual Meetings, and Department of Economics, University of Connecticut, brown-bag seminar for comments on an earlier draft of this paper. Remaining errors are my sole responsibilities.

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    References listed on IDEAS

    1. Kenneth Rogoff, 1996. "The Purchasing Power Parity Puzzle," Journal of Economic Literature, American Economic Association, vol. 34(2), pages 647-668, June.
    2. Sims, Christopher A., 1988. "Bayesian skepticism on unit root econometrics," Journal of Economic Dynamics and Control, Elsevier, vol. 12(2-3), pages 463-474.
    3. Caner, M. & Kilian, L., 2001. "Size distortions of tests of the null hypothesis of stationarity: evidence and implications for the PPP debate," Journal of International Money and Finance, Elsevier, vol. 20(5), pages 639-657, October.
    4. Papell, David H., 1997. "Searching for stationarity: Purchasing power parity under the current float," Journal of International Economics, Elsevier, vol. 43(3-4), pages 313-332, November.
    5. Dickey, David A & Fuller, Wayne A, 1981. "Likelihood Ratio Statistics for Autoregressive Time Series with a Unit Root," Econometrica, Econometric Society, vol. 49(4), pages 1057-1072, June.
    6. DeJong, David N & Whiteman, Charles H, 1991. "The Case for Trend-Stationarity Is Stronger Than We Thought," Journal of Applied Econometrics, John Wiley & Sons, Ltd., vol. 6(4), pages 413-421, Oct.-Dec..
    7. Koop, Gary, 1994. " Recent Progress in Applied Bayesian Econometrics," Journal of Economic Surveys, Wiley Blackwell, vol. 8(1), pages 1-34, March.
    8. Abuaf, Niso & Jorion, Philippe, 1990. " Purchasing Power Parity in the Long Run," Journal of Finance, American Finance Association, vol. 45(1), pages 157-174, March.
    9. Cheung, Yin-Wong & Lai, Kon S, 1995. "Lag Order and Critical Values of the Augmented Dickey-Fuller Test," Journal of Business & Economic Statistics, American Statistical Association, vol. 13(3), pages 277-280, July.
    10. Culver, Sarah E. & Papell, David H., 1999. "Long-run purchasing power parity with short-run data: evidence with a null hypothesis of stationarity," Journal of International Money and Finance, Elsevier, vol. 18(5), pages 751-768, October.
    11. 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.
    12. Ng, S. & Perron, P., 1994. "Unit Root Tests ARMA Models with Data Dependent Methods for the Selection of the Truncation Lag," Cahiers de recherche 9423, Universite de Montreal, Departement de sciences economiques.
    13. Phillips, P C B, 1991. "To Criticize the Critics: An Objective Bayesian Analysis of Stochastic Trends," Journal of Applied Econometrics, John Wiley & Sons, Ltd., vol. 6(4), pages 333-364, Oct.-Dec..
    14. Perron, Pierre, 1997. "Further evidence on breaking trend functions in macroeconomic variables," Journal of Econometrics, Elsevier, vol. 80(2), pages 355-385, October.
    15. Koop, Gary, 1992. "'Objective' Bayesian Unit Root Tests," Journal of Applied Econometrics, John Wiley & Sons, Ltd., vol. 7(1), pages 65-82, Jan.-Marc.
    16. Cheung, Yin-Wong & Lai, Kon S., 1998. "Parity reversion in real exchange rates during the post-Bretton Woods period," Journal of International Money and Finance, Elsevier, vol. 17(4), pages 597-614, August.
    17. Nelson, Charles R. & Plosser, Charles I., 1982. "Trends and random walks in macroeconmic time series : Some evidence and implications," Journal of Monetary Economics, Elsevier, vol. 10(2), pages 139-162.
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    Cited by:

    1. Thabo m. Mokoena & Rangan Gupta & Reneé Van eyden, 2009. "Testing For Ppp Using Sadc Real Exchange Rates," South African Journal of Economics, Economic Society of South Africa, vol. 77(3), pages 351-362, September.
    2. Valeria C. Castellanos, 2008. "Comisiones en cajeros automáticos y su relación con el tamaño de la red en México," Monetaria, Centro de Estudios Monetarios Latinoamericanos, vol. 0(1), pages 57-92, enero-mar.
    3. Enrique Cuervo Guzmán, 2008. "Bayesian analysis of the unit root in real exchange rates: the NAFTA case," Monetaria, Centro de Estudios Monetarios Latinoamericanos, vol. 0(1), pages 93-144, enero-mar.
    4. Hwa-Taek Lee & Gawon Yoon, 2013. "Does purchasing power parity hold sometimes? Regime switching in real exchange rates," Applied Economics, Taylor & Francis Journals, vol. 45(16), pages 2279-2294, June.
    5. César E. Tamayo & Andrés M. Vargas, 2008. "Flujos de capital y frenazos súbitos: teoría, historia y una nueva estimación," Monetaria, Centro de Estudios Monetarios Latinoamericanos, vol. 0(1), pages 27-56, enero-mar.
    6. Yong Li & Jun Yu, 2010. "A New Bayesian Unit Root Test in Stochastic Volatility Models," Working Papers 21-2010, Singapore Management University, School of Economics, revised Oct 2010.
    7. Bibiana Lanzilotta & Adrián Fernández & Gonzalo Zunino, 2008. "Evaluación de las proyecciones de analistas: la encuesta de expectativas de inflación del banco central," Monetaria, Centro de Estudios Monetarios Latinoamericanos, vol. 0(1), pages 1-25, enero-mar.

    More about this item

    JEL classification:

    • C11 - Mathematical and Quantitative Methods - - Econometric and Statistical Methods and Methodology: General - - - Bayesian Analysis: General
    • C22 - Mathematical and Quantitative Methods - - Single Equation Models; Single Variables - - - Time-Series Models; Dynamic Quantile Regressions; Dynamic Treatment Effect Models; Diffusion Processes
    • F31 - International Economics - - International Finance - - - Foreign Exchange

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