David Mangen, Ph.D., is founder and president of Minneapolis-based Mangen Research Associates, Inc. Formerly a statistics professor at the University of Southern California, Mangen is also the co-editor, with Warren A. Peterson, of Social Roles and Social Participation: Research Instruments in Social Gerontology, Volume 2, and Health, Program Evaluation, and Demography: Research Instruments in Social Gerontology, Volume 3.