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An evaluation of nearly-extinct cohort methods for estimating the very elderly populations of australia and new zealand.

Terblanche W, Wilson T - PLoS ONE (2015)

Bottom Line: However, it is recognised that estimates derived from census counts are often unreliable.Official estimates in Australia proved reasonably accurate for ages 90+ but at 100+ they varied significantly in accuracy from year to year.Estimates produced by Statistics New Zealand in aggregate for ages 90+ proved very accurate.

View Article: PubMed Central - PubMed

Affiliation: Queensland Centre for Population Research, School of Geography, Planning and Environmental Management, The University of Queensland, Brisbane, Queensland, Australia.

ABSTRACT
The rapid growth of very elderly populations requires accurate population estimates up to the highest ages. However, it is recognised that estimates derived from census counts are often unreliable. Methods that make use of death data have not previously been evaluated for Australia and New Zealand. The aim was to evaluate a number of nearly-extinct cohort methods for producing very elderly population estimates by age and sex for Australia and New Zealand. The accuracy of official estimates was also assessed. Variants of three nearly-extinct cohort methods, the Survivor Ratio method, the Das Gupta method and a new method explicitly allowing for falling mortality over time, were evaluated by retrospective application over the period 1976-1996. Estimates by sex and single years of age were compared against numbers derived from the extinct cohort method. Errors were measured by the Weighted Mean Absolute Percentage Error. It is confirmed that for Australian females the Survivor Ratio method constrained to official estimates for ages 90+ performed well. However, for Australian males and both sexes in New Zealand, more accurate estimates were obtained by constraining the Survivor Ratio method to official estimates for ages 85+. Official estimates in Australia proved reasonably accurate for ages 90+ but at 100+ they varied significantly in accuracy from year to year. Estimates produced by Statistics New Zealand in aggregate for ages 90+ proved very accurate. We recommend the use of the Survivor Ratio method constrained to official estimates for ages 85+ to create very elderly population estimates for Australia and New Zealand.

No MeSH data available.


Related in: MedlinePlus

Percentage Errors at ages 90+ for males in New Zealand in each year 1976–1996.
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pone.0123692.g016: Percentage Errors at ages 90+ for males in New Zealand in each year 1976–1996.

Mentions: In order to assess the accuracy of 90+ ERPs published by Statistics New Zealand, PEs in years 1976 to 1996 were calculated and are shown in Figs 15 and 16 (females and males respectively). PEs for variants constrained to 90+ ERPs were the same as those for ERPs and are thus not shown. From the graphs it is clear that from 1981 onwards, for both males and females, ERPs proved more accurate than estimates created from the SR, DG or SA methods. Prior to 1981, ERPs underestimated the total number aged 90+ by up to 20% for females and 33% for males. Thereafter ERPs slightly underestimated the number of females aged 90+ by up to only 3%. From 1985 the number of males aged 90+ was slightly overestimated by an average of 3.4%.


An evaluation of nearly-extinct cohort methods for estimating the very elderly populations of australia and new zealand.

Terblanche W, Wilson T - PLoS ONE (2015)

Percentage Errors at ages 90+ for males in New Zealand in each year 1976–1996.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4388836&req=5

pone.0123692.g016: Percentage Errors at ages 90+ for males in New Zealand in each year 1976–1996.
Mentions: In order to assess the accuracy of 90+ ERPs published by Statistics New Zealand, PEs in years 1976 to 1996 were calculated and are shown in Figs 15 and 16 (females and males respectively). PEs for variants constrained to 90+ ERPs were the same as those for ERPs and are thus not shown. From the graphs it is clear that from 1981 onwards, for both males and females, ERPs proved more accurate than estimates created from the SR, DG or SA methods. Prior to 1981, ERPs underestimated the total number aged 90+ by up to 20% for females and 33% for males. Thereafter ERPs slightly underestimated the number of females aged 90+ by up to only 3%. From 1985 the number of males aged 90+ was slightly overestimated by an average of 3.4%.

Bottom Line: However, it is recognised that estimates derived from census counts are often unreliable.Official estimates in Australia proved reasonably accurate for ages 90+ but at 100+ they varied significantly in accuracy from year to year.Estimates produced by Statistics New Zealand in aggregate for ages 90+ proved very accurate.

View Article: PubMed Central - PubMed

Affiliation: Queensland Centre for Population Research, School of Geography, Planning and Environmental Management, The University of Queensland, Brisbane, Queensland, Australia.

ABSTRACT
The rapid growth of very elderly populations requires accurate population estimates up to the highest ages. However, it is recognised that estimates derived from census counts are often unreliable. Methods that make use of death data have not previously been evaluated for Australia and New Zealand. The aim was to evaluate a number of nearly-extinct cohort methods for producing very elderly population estimates by age and sex for Australia and New Zealand. The accuracy of official estimates was also assessed. Variants of three nearly-extinct cohort methods, the Survivor Ratio method, the Das Gupta method and a new method explicitly allowing for falling mortality over time, were evaluated by retrospective application over the period 1976-1996. Estimates by sex and single years of age were compared against numbers derived from the extinct cohort method. Errors were measured by the Weighted Mean Absolute Percentage Error. It is confirmed that for Australian females the Survivor Ratio method constrained to official estimates for ages 90+ performed well. However, for Australian males and both sexes in New Zealand, more accurate estimates were obtained by constraining the Survivor Ratio method to official estimates for ages 85+. Official estimates in Australia proved reasonably accurate for ages 90+ but at 100+ they varied significantly in accuracy from year to year. Estimates produced by Statistics New Zealand in aggregate for ages 90+ proved very accurate. We recommend the use of the Survivor Ratio method constrained to official estimates for ages 85+ to create very elderly population estimates for Australia and New Zealand.

No MeSH data available.


Related in: MedlinePlus