expectancyyears

Expectancyyears is a term used in demography and actuarial science to describe the expected remaining years of life for an individual or a population at a given starting age. It is closely related to the conventional concept of life expectancy, but the phrasing highlights the expectation value of remaining lifespan expressed in years.

Definition and calculation: Let T be the remaining lifetime in years for a person aged a. Expectancyyears at age a is E[T]. If S(t|a) denotes the probability of surviving at least t more years given age a, then E[T|a] = ∫_0^∞ S(t|a) dt. In discrete form, E[T|a] can be computed from life-table column values by summing survival probabilities across future ages.

Relation to life expectancy: Expectancyyears is essentially the same as the standard remaining life expectancy used in life tables. It is conditional on current age and mortality patterns and may be updated as new mortality data become available.

Applications and limitations: It supports policymaking, actuarial pricing, and health economics by providing a clear measure of expected longevity. Limitations arise from changes in mortality trends over time, cohort versus period life expectancy differences, and the assumption that present mortality rates persist into the future.

See also: life expectancy, remaining life expectancy, survival analysis. Further reading includes standard texts on life tables and actuarial science.