Actuaries often refer to reductions in mortality rates as ‘mortality improvements’ although the term ‘longevity improvements’ might be more appropriate. Studies show that, over time, the average life expectancy in the UK (and most other developed countries) has increased over time: for example we expect to live significantly longer than our great-grandparents would have. The term ‘mortality improvement’ usually refers to a reduction in mortality rates (see above) – which in turn imply longer life expectancy.

The trend for longer lifespans is not tailing off, and in recent years appears to have been accelerating. Although we cannot predict with any certainty the extent to which this will continue in the future, various mathematical models have been developed. These fall into two main groups: those that extrapolate past death statistics (e.g. Lee-Carter, P-spline) and those that seek to model causes of death.