Americans are living longer on average, but most of that added life expectancy is being lived by the rich. That's according to a new paper released Monday by the National Bureau of Economic research, wherein researchers showed that this trend has helped dramatically increase the Social-security and Medicare benefits paid to the rich, while the poor have seen their benefits decline or stagnate.

Why it matters: Entitlement reformers argue that Medicare and Social Security benefits should be delayed to reflect increases in life expectancy. But these data show that such a reform would disproportionately punish poorer Americans, who are already receiving a smaller share of benefits because life expectancy gains for that group have lagged.