Parallel search for the best alternative

I wish to thank Ken Burdett, James Foster, Dale Mortensen and Kevin Roberts for many helpful suggestions. Thanks are also due to the comments of the participants at seminars at University of Minnesota, Michigan State University, Northwestern University, University of Pittsburgh, and those at the Midwestern Math Economics Conference (1989) and Econometric Society Summer Meetings (1990). Research supported by NSF Grant SES-8708325.