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008			240322b |||||||| |||| 00| 0 eng d
022			_a02664666
040			_aMSU _bEnglish _cMSU _erda
050	0	0	_aHB139.T52 ECO
100	1		_aHarvey, David I. _eauthor
245	1	0	_aUnit root testing in practice: _bdealing with uncertainty over the trend and initial condition _ccreated by 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 3
520	3		_aIn this paper we focus on two major issues that surround testing for a unit root in practice, namely, (i) uncertainty as to whether or not a linear deterministic trend is present in the data and (ii) uncertainty as to whether the initial condition of the process is (asymptotically) negligible or not. In each case simple testing procedures are proposed with the aim of maintaining good power properties across such uncertainties. For the first issue, if the initial condition is negligible, quasi-differenced (QD) detrended (demeaned) Dickey–Fuller-type unit root tests are near asymptotically efficient when a deterministic trend is (is not) present in the data generating process. Consequently, we compare a variety of strategies that aim to select the detrended variant when a trend is present, and the demeaned variant otherwise. Based on asymptotic and finite-sample evidence, we recommend a simple union of rejections-based decision rule whereby the unit root null hypothesis is rejected whenever either of the detrended or demeaned unit root tests yields a rejection. Our results show that this approach generally outperforms more sophisticated strategies based on auxiliary methods of trend detection. For the second issue, we again recommend a union of rejections decision rule, rejecting the unit root null if either of the QD or ordinary least squares (OLS) detrended/demeaned Dickey–Fuller-type tests rejects. This procedure is also shown to perform well in practice, simultaneously exploiting the superior power of the QD (OLS) detrended/demeaned test for small (large) initial conditions.
650			_aUnit root test _vTrend uncertainty _xInitial condition
650			_aAsymptotic power _vUnion of rejections decision rule
700	1		_aLeybourne, Stephen J. _eco author
700	1		_aTaylor, A. M. Robert _eco author
856			_uhttps://doi.org/10.1017/S026646660809018X
942			_2lcc _cJA
999			_c164518 _d164518