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022 _a02664666
040 _aMSU
_bEnglish
_cMSU
_erda
050 0 0 _aHB139.T52 ECO
100 1 _aHarris, David
_eauthor
245 0 0 _aTesting for a unit root in the presence of a possible break in trend
_ccreated by David Harris, David I. Harvey, Stephen J. Leybourne and A. M. Robert Taylor
264 1 _aCambridge:
_bCambridge University Press,
_c2009.
336 _2rdacontent
_atext
_btxt
337 _2rdamedia
_aunmediated
_bn
338 _2rdacarrier
_avolume
_bnc
440 _aEconometric theory
_vVolume 25, number 6
520 3 _aWe consider the issue of testing a time series for a unit root in the possible presence of a break in a linear deterministic trend at an unknown point in the series. We propose a new break fraction estimator which, where a break in trend occurs, is consistent for the true break fraction at rate Op(T−1). Unlike other available estimators, however, when there is no trend break, our estimator converges to zero at rate Op(T−1/2). Used in conjunction with a quasi difference (QD) detrended unit root test that incorporates a trend break regressor, we show that these rates of convergence ensure that known break fraction null critical values are asymptotically valid. Unlike available procedures in the literature, this holds even if there is no break in trend (the break fraction is zero). Here the trend break regressor is dropped from the deterministic component, and standard QD detrended unit root test critical values then apply. We also propose a second procedure that makes use of a formal pretest for a trend break in the series, including a trend break regressor only where the pretest rejects the null of no break. Both procedures ensure that the correctly sized (near-) efficient unit root test that allows (does not allow) for a break in trend is applied in the limit when a trend break does (does not) occur.
650 _aUnit root test
_vQuasi difference de-trending
_xTrend break
650 _aPre-test
_xAsymptotic power
700 1 _aHarvey, David I
_eco author
700 1 _aLeybourne, Stephen J
_eco author
700 1 _aTaylor, A. M. Robert
_eco author
856 _uhttps://doi.org/10.1017/S0266466609990259
942 _2lcc
_cJA
999 _c164563
_d164563