SEARCH

SEARCH BY CITATION

Keywords:

  • Seasonal unit roots;
  • structural change;
  • trend breaks;
  • LM-type unit root tests

This article proposes tests for seasonal unit roots allowing for the presence of a break in the trend slope occurring at an unknown date. In particular, new LM-type tests are derived based on the framework introduced by Hylleberg et al. (1990). Null asymptotic distributions are derived for the no break case as well as when a break is present in the data-generating process and a Monte Carlo investigation on the finite sample size and power performance of the new procedures is presented.