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 2020, mortality rates improved markedly from 2019 and there were negative excess deaths, that is, fewer deaths than expected.
- In 2021, there was a slight uptick in mortality rates, but mortality was still mostly better than before the pandemic.
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:
- At ages 85 and over, the black dot for 2022 mortality is above the index line, showing worse mortality than 2015-17. It could be that a number of these deaths were of people who had a very short expectation of life during the pandemic but lockdown kept them safe from infections.
- At ages 65-84, the black dots for 2022 are below (or just on) the index line. Although mortality was worse in this year than the previous years of the pandemic, it still wasn’t as bad as the 2015-17 average, or even 2018 or 2019.
- At ages 50-64, mortality in 2022 is again worse than the index. 2018 and 2019 were not good years either, indicating that there happened to be relatively good mortality in the index years 2015-17 for these ages.
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.
- For all ages 50 and over, the average death rate of the three years of the pandemic (2020-22) is better than the immediate prior three years 2017-19.
- For all age groups 50 and over with one exception, the average death rate of the three years of the pandemic is better than the previous three years 2015-17. The exception is age group 55-59 where the death rate for 2020-22 is slightly higher than that for 2015-17. This looks like the result of chance with both 2015 and 2017 being relatively good years for that age group.
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:
- New Zealand ranks best in the world on this analysis by Dmitry Kobak, with 155 fewer deaths than expected from the beginning of the pandemic until the end of February 2023. Of the over 50 countries in the database with latest data in the first quarter 2023, New Zealand is the only one with population over one million to still have negative excess deaths.
- Actuarial analysis of excess deaths properly allows for the changing age profile of the population over time. Actuaries in Australia estimate around 18,700 excess deaths there in total over the three years 2020-22 (updated April 2023). In the United Kingdom, actuaries estimate around 167,800 excess deaths there up to early March 2023. These estimates are lower than those by Kobak, but the relativities are consistent.
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.