Abstract
Increasing very elderly populations (ages 85+) have potentially major implications for the cost of income support, aged care, and healthcare. The availability of accurate estimates for this population age group, not only at a national level but also at a state or regional scale, is vital for policy development, budgeting, and planning for services. At the highest ages census-based population estimates are well known to be problematic and previous studies have demonstrated that more accurate estimates can be obtained indirectly from death data. This paper assesses indirect estimation methods for estimating state-level very elderly populations from death counts. A method for incorporating internal migration is also proposed. The results confirm that the accuracy of official estimates deteriorates rapidly with increasing age from 95 and that the survivor ratio method can be successfully applied at subnational level and internal migration is minor. It is shown that the simpler alternative of applying the survivor ratio method at a national level and apportioning the estimates between the states produces very accurate estimates for most states and years. This is the recommended method. While the methods are applied at a state level in Australia, the principles are generic and are applicable to other subnational geographies.
Highlights
The increase in the size of very elderly populations—defined here as those aged 85 years and above—is a demographic phenomenon occurring throughout the world [1] and one which has widespread economic and social implications
This section compares some of the results of the tests where no allowance was made for interstate migration and population estimates are based on deaths only
This paper has assessed the accuracy of a number of indirect estimation methods for creating population estimates at ages 85 and above at a state level in Australia
Summary
The increase in the size of very elderly populations—defined here as those aged 85 years and above—is a demographic phenomenon occurring throughout the world [1] and one which has widespread economic and social implications. Estimated Resident Populations (ERPs) published by the Australian Bureau of Statistics (ABS) constitute Australia’s official population estimates and are derived from census counts Such estimates tend to overestimate very elderly numbers, and the degree of overestimation is typically higher for males than females and tends to increase with age [4,5,6,7,8,9]. According to Wilson and Bell [10], official Australian population estimates provided by the ABS for ages 90 and older appear to be too high and fluctuate implausibly over time. This is a well-documented issue and not unique to Australia [11]. Because date of birth is typically verified at death, age at death is considered more reliable than age recorded on the census form, and International Journal of Population Research these indirect estimates have been shown to be very accurate when compared with population numbers in countries with population registers [5, 11, 13, 14]
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