1. Health Analysis Division, Statistics Canada, Ottawa, Ontario, Canada,
2. Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada,
3. Department of Epidemiology and Community Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada,
4. School of Social Work, McGill University, Montreal, Quebec, Canada,
5. School of Social Work, Columbia University, New York, NY, USA, and
6. Department of Paediatrics, Faculty of Health Sciences, McMaster University, Hamilton, ON, Canada