Bibliographical noteFunding Information:
A version of this paper was presented at the 57th Annual Meeting of the Western Economic Association, Los Angeles. We gratefully acknowledge very helpful comments of anonymous referees and the research and computational assistance of Brian & m e l s and Tom Clifton. Brofessor Zaidi's study was partly supported by the Australian Graduate School of Management and partly by the Single Quarter Leave Programme of the University of Minnesota for which he wishes to express his gratitude. Brofessor Siebert wishes to acknowledge support from the Department of Economics, The University of Iowa.