First Author:   Jacques SILBER Bar-Ilan University jsilber_2000@yahoo.com   Department of Economics, Bar-Ilan University Ramat-Gan, 52900, Israel   97235318345(Phone) 97235318345(Fax) http://www.biu.ac.il/soc/ec/silber/silber.htm#C Second Author: Michal Weber Bar-Ilan University Weberm@mail.biu.ac.il   Department of Interdisciplinary Studies, Bar-Ilan University Ramat-Gan, 52900, Israel   0525237770(Phone)