Should Projections of Mortality Improvements be Subject to a Minimum Value?

Projections of future mortality typically used for funding pension scheme liabilities assume that future year-on-year decreases in mortality rates will slow rapidly, and that there is very limited potential for further decreases at the oldest ages. This paper considers the consistency of such projections with current trends in life expectancy. Particular focus is paid to whether future mortality should be subject to a minimum level of improvement to reflect general advances in medicine. Care is taken to exclude the additional increases in longevity arising from a concentration of positive health factors amongst the generation who are currently experiencing the ‘cohort effect’. If historic trends continue into the future, then period life expectancy from age 65 in England & Wales will increase at 26 days p.a. for women and 41 days p.a. for men, with additional increases arising from the ‘cohort effect’. This is a faster rate of period increase in life expectancy than embedded in the interim cohort projections. One way to ensure that actuarial projections keep pace with the population trend is to subject projections to a minimum level of (geometric) improvement of at least 11/4% p.a. for men and 3/4% p.a. for women, at all older ages and in all future years. Consideration is given to the possible impact of differences between the socio-economic profile of England & Wales and the membership of the pension schemes to whom the projections will be applied ultimately. This paper also highlights that the application of a single minimum value, independent of time and age, simplifies a more complex underlying pattern, but that minimum improvements of 11/4% p.a. for males and 3/4% p.a. for females represent an average of historic improvements in mortality seen in England & Wales. The paper includes a survey of the history of the low levels of mortality seen currently. The survey includes some discussion on the potential for future improvements and considers topical issues, such as the potential impact of obesity on life expectancy projections (and, in turn, the minimum value applied to improvements). The financial impact of subjecting projections of mortality improvement to a minimum value is quantified.