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Unit‐root testing: on the asymptotic equivalence of Dickey–Fuller with the log–log slope of a fitted autoregressive spectrum
Author(s) -
Ioannidis Evangelos E.
Publication year - 2010
Publication title -
journal of time series analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.576
H-Index - 54
eISSN - 1467-9892
pISSN - 0143-9782
DOI - 10.1111/j.1467-9892.2010.00652.x
Subject(s) - mathematics , autoregressive model , unit root , equivalence (formal languages) , spectrum (functional analysis) , unit root test , statistics , pure mathematics , cointegration , physics , quantum mechanics
In this article we consider the problem of testing for the presence of a unit root against autoregressive alternatives. In this context we prove the asymptotic equivalence of the well‐known (augmented) Dickey–Fuller test with a test based on an appropriate parametric modification of the technique of log‐periodogram regression. This modification consists of considering, close to the origin, the slope (in log–log coordinates) of an autoregressively fitted spectral density. This provides a new interpretation of the Dickey–Fuller test and closes the gap between it and log‐periodogram regression. This equivalence is based on monotonicity arguments and holds on the null as well as on the alternative. Finally, a simulation study provides indications of the finite‐sample behaviour of this asymptotic equivalence.