Baseline longevity (or current longevity)
\ˈbeɪˌslaɪn\ \lɔnˈʤɛvəti\
A snapshot of current longevity captured by a base table.
Baseline longevity is a measure of how long people will live if nothing changes in the future (for example, no medical advances or changes to lifestyle).
When calculating how long you expect people to live, a good strategy is to first calculate baseline longevity as accurately as possible, and then overlay an assumption of how things will change in the future.