Local asymptotic power of the Im-Pesaran-Shin panel unit root test and the impact of initial observations
In this note we derive the local asymptotic power function of the standardized averaged Dickey-Fuller panel unit root statistic of Im, Pesaran and Shin (2003, Journal of Econometrics, 115, 53-74), allowing for heterogeneous deterministic intercept terms. We consider the situation where the deviation of the initial observation from the underlying intercept term in each individual time series may not be asymptotically negligible. We find that power decreases monotonically as the absolute values of the initial conditions increase in magnitude, in direct contrast to the univariate case. Finite sample simulations confirm the relevance of this result for practical applications, demonstrating that the power of the test can be very low for values of T and N typically encountered in practice.
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- Pasaran, M.H. & Im, K.S. & Shin, Y., 1995.
"Testing for Unit Roots in Heterogeneous Panels,"
Cambridge Working Papers in Economics
9526, Faculty of Economics, University of Cambridge.
- Evans, G B A & Savin, N E, 1981. "Testing for Unit Roots: 1," Econometrica, Econometric Society, vol. 49(3), pages 753-79, May.
- Ulrich K. M¸ller & Graham Elliott, 2003. "Tests for Unit Roots and the Initial Condition," Econometrica, Econometric Society, vol. 71(4), pages 1269-1286, 07.
- David I. Harvey & Stephen J. Leybourne, 2005. "On testing for unit roots and the initial observation," Econometrics Journal, Royal Economic Society, vol. 8(1), pages 97-111, 03.
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