1. Cancer Epidemiology Centre; Cancer Council Victoria; Melbourne 3004 Victoria Australia
2. Farr Institute of Health Informatics Research; London NW1 2DA United Kingdom
3. Department of Medical Statistics; London School of Hygiene & Tropical Medicine; London WC1E 7HT United Kingdom
4. Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health; University of Melbourne; Victoria Australia