Comparing migration in Britain and Australia: harmonisation through use of age – time plans

Differences in the way migration is measured impede cross-national comparisons of internal migration. In this paper we utilise age – time diagrams to elucidate these problems for Australia and the United Kingdom and present solutions which generate time series of interregional migration for the two countries, harmonised with respect to age – time plans. We achieve this through estimation of the numbers of migration transitions (Australia) or migration events (Britain) for common age – period – cohort (APC) spaces. We derive appropriate population stocks for computation of transition probabilities or occurrence-exposure rates. In the final section of the paper we present a series of migration-intensity calculations based on varying combinations of period – cohort, period – age, and age – period – cohort perspectives, to demonstrate the significance of the variations, and the errors that can arise without harmonisation.