1. The relevant life expectancy is life expectancy at or near retirement age. Falling infant mortality doesn’t make a case for delaying Social Security — and that’s important, because gains have been much less striking at age 65 than at birth.
2. Gains in life expectancy have been very strongly correlated with income and class; those with lower incomes and lower status — the very people who depend most on Social Security — have seen very small gains in life expectancy: