[1] Penn State Univ, Dept Human Dev & Family Studies, 119 Hlth & Human Dev Bldg, University Pk, PA 16802 USA
[2] Univ Michigan, Inst Social Res, POB 1248,426 Thompson St, Ann Arbor, MI 48106 USA
[3] Univ Texas Austin, Sch Human Ecol, Dept Human Dev & Family Sci, 200 W 24th St,Stop A2700, Austin, TX 78712 USA