Mortality

Life expectancy at birth in a particular year is a way of summarising age-specific mortality rates in that year. This means that if mortality rates are falling, then life expectancy will be rising. Under Statistics New Zealand’s medium assumptions, the median male life expectancy at birth rises from 76.3 years in 2000 to 83.5 years in 2050, while median female expected longevity grows from 81.1 years to 87.0. Overall, this means a gain of 1.3 years per decade, on average.

This rate of gain is slower than we have seen in the past half century (eg, female longevity grew by 9.8 years from 1950 to 2000 but is expected to grow by only 5.9 years in the next half century). For those aged 65 and 85, the assumed life expectancy gains are generally greater than the historical growth.

Figure 4.4 shows life expectancy at birth since 1890, while Table 4.1 includes life expectancy at birth as well as at different ages.

Source: Human Mortality Database, Statistics New Zealand medium mortality assumptions

Source: Life expectancy at birth from Statistics New Zealand, medium mortality assumption

Alternative mortality paths

As with fertility, Statistics New Zealand has produced projections based on two alternative assumptions of the future course of mortality: high mortality, where life expectancy in 2050 is 81.0 and 85.0 for men and women respectively; and low mortality, where life expectancy is 86.0 and 89.0 for men and women respectively.

There are two particular features of this increase in life expectancy.

First, there has been a substantial reduction in infant mortality. In 1900, for example, 8% of non-Ma¯ori children (born alive) would be expected to die before their first birthday. By 2003, this had fallen by a factor of almost 16 to 0.49%. Similar reductions have occurred at all ages up to 10.

Second, death rates have also reduced substantially during the middle stages of life. Although the reduction is not as dramatic as in the early years of life, it is still substantial: in the order of four to eight times lower in 2003 than in 1900.

Source: Statistics New Zealand

The combination of the lower death rates in early and middle age and little movement in the oldest age to which people live results in what demographers refer to as a “rectangularisation” of the survival chart: far more people survive into old age, and indeed into very old age, but the oldest age to which people are living is increasing at a slower rate (see Figure 8.3).

While mortality trends are clear, as yet we do not have full knowledge of what is causing this decline in death rates, what sorts of lives people are leading, especially in later life, and whether the trends of the recent past will continue or reverse. Chapter 6, which deals with health spending, contains an extended discussion of the drivers of mortality.

This Statement uses Statistics New Zealand’s medium mortality assumption to drive the base-case projections. This may be on the conservative side (relatively low longevity outcomes) compared with some assumptions being used by other agencies in their long-term work.

Statistics New Zealand’s low mortality (higher longevity) assumption has a greater proportion of elderly, a relatively smaller labour force, and a larger population by 2050 (up by 2.3%). This is likely to place more pressure on the fiscal position.

An assumption of high mortality (lower life expectancy) will reverse these differences relative to the base case. The labour force would be proportionately larger, while the population in 2050 would be smaller.