Template-Type: ReDIF-Article 1.0 Author-Name: Antonio Aguirre Author-Workplace-Name: Universidade Federal de Minas Gerais (UFMG) Author-Name: Andreu Sansó Author-Workplace-Name: Universidad de Barcelona Title: Using different null hypotheses to test for seasonal unit roots in economic time series Abstract: This paper tries to make a contribution by discussing the application of different testing procedures to determine the seasonal properties of quarterly data. We focus on the Hylleberg et al. and on the Canova-Hansen tests. The former detect a unit root at the zero frequency but no seasonal unit roots. The latter reveal that the series displays a statistically significant seasonal pattern with changing coefficients of some seasonal dummy variables. The CH tests finding of a seasonal unit root at frequency ? does not agree with the HEGY-type test results. An explanation is given to try to interpret these two contradictory outcomes. Classification-JEL: C4 Journal: Económica Pages: 3-26 Volume: XLVIII Issue: 1-2 Year: 2002 Month: January-December File-URL: https://revistas.unlp.edu.ar/Economica/article/view/8513/7061 File-Format: Application/pdf Handle: RePEc:akh:journl:525