First Author:   Wiji Arulampalam University of Warwick wiji.arulampalam@warwick.ac.uk   Department of Economics, University of Warwick Coventry, CV4 7AL, United Kingdom   44 (0)24 7652 3471(Phone) 44 (0)24 7652 3471(Fax) http://www.warwick.ac.uk/Economics/arulampalam Second Author: Wiji Arulampalam University of Warwick res2002@warwick.ac.uk   Department of Economics, University of Warwick Coventry, CV4 7AL, United Kingdom       http://www.warwick.ac.uk/res2002