Paper presented at the Final Int. Conf. of the ESF Scientific Network on Household Panel Studies held CEPS/INSTEAD Walferdange (LU) 1-2 Jun 1993Available from British Library Document Supply Centre- DSC:9349.2264(ESF-ESNHPS-WP--87) / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo