Population estimates and projections for Australia’s very elderly population at state and national level

Abstract

As in many developed countries, the very elderly population (ages 85+) is the fastest growing age group in Australia, with far-reaching economic and social consequences. To effectively plan and budget for the income, aged care and health care needs of the very elderly, accurate estimates and projections are required. There are, however, several obstacles relating to the availability and accuracy of very elderly data. Official population estimates at very high ages in Australia have been found to be too high and fluctuate implausibly over time. International and local studies have found large errors in projected very elderly populations, stemming from inaccurate mortality rate forecasts.This thesis aims to create accurate estimates and projections for Australia's very elderly population at a state and national level. Various methods for estimating very elderly populations from death counts were assessed for accuracy at both a national and state level.While the Human Mortality Database uses such methods to create estimates for many countries, their accuracy has never been assessed for Australia. Furthermore, little is known, locally or internationally, about their performance at a sub-national scale. In this study, the accuracy of various nearly-extinct-cohort methods were assessed at the Australian national and state level by retrospectively applying them to extinct cohorts and comparing the results against those obtained from applying the Extinct Cohort method. Suitable methods were applied to create very elderly population estimates and death rates for Australia from 1972-2012 by sex, state and at single ages 85-110+. The growth, changes in the age-sex composition and the demographic drivers of growth of Australia's very elderly population were analysed. Based on these estimates, more reliable death rates were calculated, allowing a detailed study of the changing patterns and trends in Australian adult mortality. Finally, a number of mortality forecasting methods were retrospectively evaluated for their accuracy in projecting adult death rates for Australia over 10 and 20 years ending in 2012. An appropriate method was applied to create projections for the next three decades.It was found that, compared to the official census-based estimates, more plausible and accurate estimates, especially for ages 95+, could be derived from death counts. The Survivor Ratio (SR) method with results constrained to official estimates for ages 85+ produced accurate very elderly population estimates for Australia across the sexes and ages at both a national and state level. Internal migration is sufficiently minor to be ignored. Very accurate state-level estimates could also be derived using a simpler method of apportioning national single-age estimates between the states. Adult death rates in Australia were found to show consistent and regular patterns of decline since the 1970s, with rates of decline decreasing with age. These patterns support the use of simple direct extrapolation methods for forecasting. The Geometric,...

The rapid growth of Australia’s advanced age population

“…The method assumes death counts are accurate and complete, and that net overseas migration is negligible at the highest ages. These are reasonable assumptions in Australia (Jdanov et al 2008;Terblanche 2015). Deaths data were obtained from the Australian Bureau of Statistics' ABS.Stat tool (http://stat.data.abs.gov.au/) and customised ABS data orders.…”

“…Demographic research over the last 20 years has proven these types of methods to be highly effective in creating more accurate population numbers of the oldest old than those based on 3 the census (Thatcher et al 2002;Terblanche 2015). A simple Excel/VBA workbook implementing these methods is available from the authors on request.…”

“…None of these data sources and assumptions are perfect. The quality of deaths data has been judged as reasonable since the 1970s, although less good prior to that(Jdanov et al 2008;Terblanche 2015). The decomposition is additionally dependent on reliable historical births data, and these data may also be subject to some degree of under-coverage, particularly amongst the Aboriginal and Torres Strait Islander population.We encourage the Australian Bureau of Statistics to produce official population estimates at the highest ages using the Extinct Generation and Survivor Ratio methods.…”

A brief guide to producing a national population projection

“…2) Prepare your own mortality projections. National mortality forecasting has received the greatest amount of attention in demographic forecasting research and there is no shortage of methods (Booth and Tickle 2008;Ediev 2020;Terblanche 2015) and software (e.g., Hyndman et al 2019;Sevcikova et al 2019) to choose from.…”

Evaluation of simple methods for regional mortality forecasts

“…And in many countries, populations in these age groups are growing rapidly (UN 2017a ), as a result of larger cohorts flowing through to the older ages and declines in older adult mortality. The growth of the elderly population has important implications for governments, business, society, families, and the very old themselves (Australian Government 2015 ; Beard et al 2012 ; Terblanche 2015 ; UN 2017b ). Recent advances in mortality forecasting methods hopefully mean that today’s mortality forecasts are the most reliable ever (‘hopefully’ because we cannot be absolutely sure until forecasts are compared with actual outcomes many years into the future).…”