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New Zealand mortality – after the pandemic

New Zealand had one of the lowest levels of excess mortality in the world in 2020 and 2021 because it held Covid-19 at bay until the population was well-vaccinated. What is happening now?

The experience in most developed countries over recent decades has been that death rates have improved steadily over time, meaning that each generation will live longer on average than older generations. Covid-19 disrupted the improvement trend.  This post shows that Covid affected population mortality in Aotearoa New Zealand in a uniquely benign way, which lends support to a future of continuing longer lives.

Previous posts have shown that mortality in Aotearoa New Zealand during the first two years of the pandemic was extraordinarily light, especially compared to the experience of many other countries. 

In 2022, borders were reopened and restrictions stepped back.  As at March 2023, people with Covid-19 still need to self-isolate for seven days.

In 2020 and 2021, there were fewer than 50 deaths attributed to Covid-19. As at mid-March 2023, there have been fewer than 4,000 deaths within 28 days of a positive Covid test in total through the pandemic years, 2,600 attributed to Covid, from a population of 5.2 million.

Looking back at past death rates: pandemic blip

Death rates (also called mortality rates) count the number of deaths in a year at a specific age as a proportion of the number of people alive at that age.  The history of death rates for the over-50s in New Zealand shows a steady fall, although there are fluctuations due to seasonal impacts and random variations.

It’s useful to index changes in death rates over time to a specific period.  The index period chosen here is the average of 2015-17; before the pandemic and averaging over three years to smooth out any oddities in a single year.  The choice of years is simply to show what happened through a couple of normal years before the pandemic as well as the pandemic years of 2020-22.

For all ages, the blue dots representing the 2020 and 2021 are below the index line, because death rates were better than in previous years – the result of lockdowns, border management and very little Covid or influenza.

What happened in 2022 varied by age:

A simple view of the overall effect of the pandemic on mortality is given by comparing the average death rates for each age group during the three years of the pandemic with prior three-year periods 2015-17 and (for a further check) with 2017-19.

In other words, the pandemic did not send the long-term trend of mortality improvement at ages over 50 off course.  It seems to have been a blip, not a trend.

New Zealand’s number one ranking

Another way to answer the question of the overall impact of the pandemic on mortality is to estimate “excess deaths”.  Various trackers of the number of deaths (from all causes) that were judged to be excess to those expected if the pandemic had not occurred were started soon after the pandemic hit. Most of these trackers have now stopped.

Although the various trackers use different methods, and the numbers of excess deaths they calculate are approximations, they are still useful indicators. The excess deaths calculation does not require decisions on whether deaths were due to Covid or associated issues or were not Covid-related. Excess deaths is an intuitively simple measure that neatly summarises the overall impact of the pandemic on life or death.

From some ongoing trackers:

Aotearoa New Zealand has always been recognised as one of few countries which avoided excess deaths in 2020 and 2021.  Comparisons with other countries show New Zealand consistently having negative cumulative excess mortality  over the pandemic.  It now appears to be in the unique position of the additional deaths of 2022 and early 2023 being about on par with the deaths ‘saved’ during the first two years of the pandemic. Compared to the mortality experiences in other countries, with significant counts of excess deaths, Covid-19 in Aotearoa New Zealand has been benign. 

Looking forward: Death rates still improving

To make projections of the size of the future population of Aotearoa, StatsNZ make their best estimates of how many people will come to or leave the country in future.  This requires estimates of fertility (how many babies are born), migration (in and out) and deaths at each age in each future year. 

The projected death rates in the chart below tell us StatsNZ’s modelled estimate of mortality trends in future. The long-term trend is expected to return to a decline in death rates at all ages (including those younger ages not shown on the chart with lower absolute levels of death rates).

For this latest estimate, StatsNZ assumed a more gradual decrease in death rates than in their previous (2020-base) projections. But the slowdown is not due to Covid-19. Developed countries showed signs of slowing the rate of assumed future mortality improvement, even before the pandemic.

New Zealand mortality is expected to keep improving after the pandemic blip which means longer lives expected on average for each generation.  The chart below shows this as average lifespans for the population of Aotearoa born from 1950 onwards, from birth and from their 65th birthday, sourced from StatsNZ latest update on cohort life expectancy.

Average lifespans are expected to increase gradually for each generation. This is a reminder of the optimistic outlook for longer lives despite the pandemic and other health challenges. However, noting that this analysis is all about the average of the population, it is also a call to work for equitable health outcomes across the whole population.




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