In this paper it is demonstrated by simulation that, contrary to a widely held belief, pure seasonal mean shifts - i.e., seasonal structural breaks which affect only the deterministic seasonal cycle - really do matter for Dickey-Fuller long-run unit root tests.

The purpose of this paper is to test both short- and long-run implications of the (rational) expectations hypothesis of the term structure of interest rates using Portuguese data for the interbank money market. The results support only a very weak, long-run or "asymptotic" version of the...