New Zealand longevity update, 2021

New data gives new estimates for how long New Zealanders might live.  The trends haven’t changed: later generations live longer than earlier, and retirement planning should still consider a likely lifespan to age 90 to 95.

Previous estimates of the longevity of the New Zealand population used data published by StatsNZ in 2019. The latest update is from April 2021.  This shows life tables for each cohort of New Zealand population born from 1876 to 2019, a hugely valuable resource.

A cohort life table shows the average mortality experience of a group born in a specific year. For a cohort in which everyone is now dead, we know how many lived to each age.  From that data we can chart the distribution of lifespans achieved in that cohort, and calculate indicators such as average lifespan, the median age at death, the most common age at death, and the age to which at least one in five people lived to. For cohorts born more recently so that some people are still alive, StatsNZ uses estimates of future mortality to complete the cohort experience and allow charts to be drawn and indicators to be calculated to describe likely outcomes.

A word on indicators

Previous posts have discussed the use of different indicators.  Most importantly:

Cohort life expectancy is a measure of average lifespan because it uses information on how death rates are expected to change over time, as people go through their lives.  It is the average length of life left at a given age for a group of people born in the same year, based on expected future average death rates for the population.

The life expectancy indicator most referred to in general articles or news reports is “period life expectancy”. This measures average mortality between populations at a point in time, so is not useful for indicating how long people might live.

Life expectancy (even when using cohort life expectancy) is not the best or only measure of how long, typically, people live.  It’s an average of a skewed distribution and is always on the low side. Other measures such as median or modal age at death give more information on the actual shape of the distribution. The age to which, say, one in five live indicates the chances of living to the oldest ages.  This is especially important for considering longevity risk – the risk of running out of money because of living longer than expected.

If considering how long people might live while receiving NZ Super, the public pension in New Zealand, then the indicators of note are those of NZ population cohorts born in different years who survived to the age of eligibility, that is, age 65 (or are expected to do so in the case of younger cohorts).

How long will New Zealanders live?

The key charts are here for cohorts reaching age 65 in 2021, and twenty years before or after.  The 3 cohorts represent current older retirees, those now around the age when most people retire or step back from work, and those probably thinking of retirement in a couple of decades.

The key indicators have not changed significantly from previous estimates, and the key messages still stand:

  • Women, on average, live longer than men.
  • Lifespans are getting longer for each successive cohort.
  • Ages at death are becoming more similar – fewer people dying below age 80 as the peak of the distribution becomes more pointed – but uncertainty in age at death is extending to higher ages as the distribution extends to the right.
  • People in their 40s or older can use an estimate for their likely lifespan of 25 to 30 years after age 65 (to age 90 to 95).

What does it mean for me?

A woman reaching her 65th birthday in 2021 belongs to a cohort which, counting everyone born in the same year, has an average expected lifespan of 83 years.  But those who survive to age 65 can expect to live on average to age 89, and half of them to at least age 90.  The most common age at death is expected to be 92.  Two in five can expect to live to at least age 95. dx cohort 1956 female June21

Improvements continue steadily for younger cohorts, so that a daughter of the woman born twenty years later, on reaching age 65, can add one or two years to each of those indicators. A man of the same ages can reduce the indicators by two or three years.

Individuals will have their own risk factors, known or unknown.  Individual longevity experience depends on many risk factors, as well as luck.  Population longevity is only a guide to individual prospects, but as longevity keeps on increasing, so does the risk that people underestimate their own longevity chances. To keep longevity risk at bay, we need to keep up to date with estimates for how long we might live.

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