This Just One Minute post describes some of the questionable actuarial assumptions being made by Social Security:
extraordinary data-dive into the workings of the Social Security Trust Fund life-span estimation process. Their conclusion - the Social Security actuaries are using outmoded techniques; contemporary analytical tools suggest that Americans will live longer and deplete the (notional) Social Security Trust Fund faster than currently forecast. Properly adjusted forecasts would show Social Security spending an additional $800 billion (cumulatively) by 2031, which is roughly $40 billion per year.
And the authors discover a real howler - apparently the Mayans have found a toehold in the Social Security office:
So fifteen years from now everyone aged 55-59 will die? This has to be a blow to current 40-44 year olds. Geez, all those folks walking around reassuring themselves that life begins at 40 now find it will end in the late 50's. I'd say don't blame me, I voted for Romney, but I am sure this is a bipartisan methodlogical whoopsie.