The objective of this paper is to apply the mis-specification (M-S) encompassing perspective to the problem of choosing between "linear" and "log-linear" unit-root models. A simple M-S encompassing test, based on an auxiliary regression stemming from the conditional second moment, is proposed...

Dickey and Fuller ["Econometrica" (1981) Vol. 49, pp. 1057-1072] suggested unit-root tests for an autoregressive model with a linear trend conditional on an initial observation. T"Power of tests for unit roots in the presence of a linear trend"ightly different model with a random initial value...