People also live longer. Social security (retirement) was never intended to support people for 30-40 years. The age has to go up with the life expectancy to keep it solvent.
"What’s remarkable, however, is how much life expectancy increased between 1990 and 2010 in counties of all poverty levels"
http://marginalrevolution.com/marginalrevolution/2016/05/the...
http://www.vox.com/2016/4/11/11405954/health-life-expectancy...
The 2000-2010 increase in your source is ~2 years for the poorest men and ~1 year for the poorest women. The 2001-2014 increase in my source is ~.3 for poor men and ~0 for poor women.
That seems like a really big gap, and I don't have a good way to reconcile them.
http://www.vox.com/2016/4/11/11405954/health-life-expectancy...
Disability or other welfare, maybe, but that would be different.