Most people who get retirement benefits from Social Security get the bulk of their income from their monthly benefits. Because they don't have many other sources of money to pay for living expenses, the annual cost-of-living adjustments (COLAs) that Social Security gives participants every January play a vital role in helping people make ends meet -- especially as the expenses they have to pay inexorably rise.Over the past decade, Social Security has been pretty stingy in the COLAs it gives to retirees.