1. Department of Public Health and Primary Care, Leiden University Medical Center, Leiden, The Netherlands
2. Department of General Practice & Nursing Home Medicine, VU University Medical Center, Amsterdam, The Netherlands
3. Department of Primary and Community Care, Radboud University Medical Center, Nijmegen, The Netherlands
4. Netherlands Institute for Social Research, Hague, The Netherlands
5. Department of Sociology, Vrije Universiteit, Amsterdam, The Netherlands