Probabilistic population forecasting for subnational regions: a case study of South East Queensland, Australia
Tom Wilson, University of Queensland, Australia
Date: Tue, 5 July 2011 , Time: 10:00 - 11:00
Over the last two decades significant progress has been made in the development of probabilistic population forecasting methods, and many applications to countries and global regions are now in evidence. Unfortunately little interest has been shown in the extension of these methods to subnational areas (and other disaggregations of national populations). Given that forecast error is inversely related to population size, coupled with the fact that much planning occurs at the local and regional scale, the need to quantify forecast uncertainty for subnational regions is arguably even greater than at the national scale. In addition to uncertainty surrounding fertility, mortality and international migration, subnational projections are compromised by the volatile nature, and hence the limited predictability, of internal migration. This paper presents a regional probabilistic population and household projection for the rapidly growing region of South East Queensland, a metropolitan region of about 3 million people in eastern Australia. A bi-regional framework is adopted consisting of the region of interest and the rest of the country; predictive intervals for fertility, mortality, migration and living arrangements are formulated on the basis of time series models, past errors and expert judgement. The results demonstrate the considerable extent of forecast uncertainty for the region, and reveal how the official high-low projection range provides a misleading, and rather narrow, indication of uncertainty. The paper concludes by discussing how probabilistic forecasts might be applied in metropolitan regional planning.
About the presenter
Tom Wilson was appointed a Senior Research Fellow in demography at the University of Queensland in August 2009, having previously been Principal Demographer for the New South Wales Department of Planning with responsibility for the State’s population and household projections. His research interests include population projections (especially multiregional and probabilistic modelling), population estimation techniques, population ageing, migration modelling, Indigenous demography, and regional and local demographic change. He was awarded his PhD in population geography in 2001 by Leeds University in the UK.