An analysis of where older Americans get their income finds Social Security is a key source, keeping about 15 million above the poverty line, the AARP Policy Institute said.

The analysis of 2012 data found that 84 percent of older Americans, representing 36 million of those 65 and older, received Social Security payments. The average amount of benefits received was $14,229. The average annual income for everyone in the age group was $31,742. But for half of all elderly, the figure was less than $19.604.

For all retirees, Social Security represented 37.7 percent of income, but the varying importance of the benefits was apparent when earners were divided into five groups.