1. Section of Social Medicine; Department of Public Health, University of Copenhagen; Oster Farimagsgade 5, POB 2099, DK-1014 Copenhagen K Denmark
2. Danish Cancer Society Research Center; Strandboulevarden 49, DK-2100 Copenhagen O Denmark
3. Statistics Denmark; Sejrøgade 11, DK-2100 Copenhagen O Denmark
4. Section of Biostatistics; Department of Public Health, University of Copenhagen; Oster Farimagsgade 5, POB 2099, DK-1014 Copenhagen K Denmark