This paper proposes two new unit root tests that are appropriate in the presence of an unknown number of structural breaks. One is based on a single time series and the other is based on a panel of multiple series. For the estimation of the number of breaks and their locations, a simple...

In this paper we discuss the differences between the average marginal effect and the marginal effect of the average individual in sample selection models, estimated by Heckman's two step procedure. We show that the bias that emerges as a consequence of interchanging them, could be very...