1. Survey Research Center , University of Michigan-Ann Arbor , 4118 Institute for Social Research, 426 Thompson Street, Ann Arbor, MI , 48106 , U.S.A.
2. Institute for Employment Research , Regensburger Strasse 104, Nuremberg , 90478 , Germany .
3. Walter R. McDonald & Associates , 12300 Twinbrook Pkwy, Suite 310, Rockville , MD 20852 , U.S.A.