This Smart Money article
offers an interesting look inside insurance companies as they plan their life and annuity policies:
Call it the new death calculus: the 21st-century equation for determining human longevity. Or call it misguided guesswork, as some critics have. Either way, it's hard to imagine a math problem that has flummoxed humanity for longer. (Actuaries, in fact, have been fumbling for an answer since 1583, when the first life insurance policy was issued.) And it's even harder to conceive of one with more at stake in the outcome.
Leaving aside the matter of Social Security -- a 14-digit-dollar question of its own -- the pool of money tied to the death calculus is somewhere on the order of $27 trillion.