1. Department of Biostatistics, School of Public Health; University of Michigan; Ann Arbor MI 48109 U.S.A.
2. Arbor Research Collaborative for Health; Ann Arbor MI 48104 U.S.A.
3. Department of Economics and Center for Policy Research, Maxwell School of Citizenship and Public Affairs; Syracuse University; Syracuse NY 13244 U.S.A.
4. Departments of Epidemiology, Environmental Health Sciences, and Urology; University of Michigan; Ann Arbor MI 48109 U.S.A.
5. Department of Medicine; University of Michigan; Ann Arbor MI 48109 U.S.A.