1. Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA;
2. Department of Health Systems Science, Kaiser Permanente Bernard J. Tyson School of Medicine, Pasadena, CA;
3. Division of Research, Kaiser Permanente Northern California, Oakland, CA;
4. Mid-Atlantic Permanente Research Institute, Kaiser Permanente Mid-Atlantic States, Rockville, MD;
5. Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute, Boston, MA; and
6. Department of Epidemiology and Biostatistics, UCSF, San Francisco, CA.