Life expectancy in 1900 was 47. In 1935 (when the Social Security program became an active policy), life expectancy had increased to 61. The Social Security full retirement age (FRA) at that time was 65, meaning that over 50% of Americans were never intended to receive any sort of retirement benefit from the Social Security program. Life expectancy is up to 78.7 as of 2017. (source: U.S. Census Bureau).