1. Population Research Center and Institute of Metropolitan Studies, Portland State University, P.O. Box 751, Portland, OR 97207, USA
2. Department of Public Health and Preventive Medicine, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Mail Code CB 669, Portland, OR 97239, USA
3. Kaiser Permanente Center for Health Research, Northwest/Hawaii, 3800 N. Interstate Avenue, Portland, OR 97227, USA
4. Metro Data Resource Center, 600 NE Grand Avenue, Portland, OR 97232, USA
5. Department of Epidemiology and Biostatistics, Drexel University School of Public Health, 1505 Race Street, MS 1033, Philadelphia, PA 19102, USA