Our traditional instruments for measuring population can no longer cope in a society that has become more mobile, less accessible and less willing to respond to surveys. Counting immigrants in cities is presenting big challenges. New instruments are needed.

I believe the future lies in a Nordic-style population register holding only core details of every resident and providing the base for all public agencies' personal records. Core details are name, address, sex, date and place of birth and a personal reference number. The register would generate reliable annual population statistics, both national and local.