Unit root testing against an ST–MTAR alternative: finite-sample properties and an application to the UK housing market

Abstract

A class of smooth transition momentum-threshold autoregressive (ST–MTAR) tests is proposed to allow testing of the unit root hypothesis against an alternative of asymmetric adjustment about a smooth nonlinear trend. Monte-Carlo simulation is employed to derive finite-sample critical values for the proposed test and illustrate its attractive power properties against a range of stationary alternatives. The empirical relevance of the ST–MTAR test is highlighted via an application to aggregate house price data for the UK. Interestingly, house prices are found to exhibit structural change characterized a fitted logistic smooth transition process, with the newly proposed ST–MTAR test providing the most significant results of the alternative smooth transition unit root tests available.