Using Bayesian Models To Forecast International Arrivals And Departures By Age, Sex, And Region In New Zealand

Statistics New Zealand prepares regular population projections at the subnational level. Like other statistical agencies, Statistics NZ currently uses a deterministic approach to subnational projections. However, we are currently developing an alternative, more statistical, approach. In this paper, we describe two Bayesian hierarchical models for estimating and forecasting international in-migration and out-migration rates, disaggregated by age, sex, and territorial authority. The model uses international arrivals and departures data for 1991-2013, and produces forecasts for 2014-2039. Special attention is given to the ability of the model to estimate migration rates for small population domains. The modelled approach provides a coherent and integrated measure of uncertainty at the detailed demographic level. Examples of estimated and forecasted migration rates are presented. We conclude with a discussion of the challenges and limitations of the data and model, and directions for future developments.