It's not so simple...
"The change in overall life expectancy mostly reflects lower infant mortality, not longer lifespans for adults.
In 1939, infant mortality rates were extremely high, but once age 65 the average American could expect to live another 13.4 years, or to age 78. Today, better health care and fewer infant deaths means overall life expectancy has gone up. But life expectancy after age 65 - a more accurate way to predict how long people are really living in retirement - hasn't changed nearly as much.
As of 2008, the average American who makes it to age 65 could expect to live 19.6 years. That's just 6 years longer than in 1939, and less than 2 years longer than in 1979 - and even that number overgeneralizes, because it ignores other factors that affect life expectancy, including gender, race, and income. A Social Security Administration study found income inequality plays a big role in life expectancy. For workers in the top half of the earnings distribution, average life expectancy is 86.5, but for those in the bottom half it's just 81 - a gap of more than 5 years that continues to grow.