Washington ? Social Security beneficiaries will get a 2.1 percent cost-of-living increase next year, providing an extra $19 a month for the typical retiree.

Next year’s boost, announced Thursday by the Social Security Administration, is up from this year’s increase of 1.4 percent, but still reflects an economy with low inflation.

The cost-of-living adjustment, or COLA, begins in January and covers more than 51 million Americans. It is tied to an index of consumer prices, the government’s chief measure of inflation.

Monthly benefit checks have been adjusted automatically since 1975 to protect retirees’ income from erosion by rising inflation.

“The weak stock market and low fixed-income rates on one hand and rapidly rising health care costs on the other have reinforced the importance of Social Security in the last few years,” said Bill Novelli, executive director and chief executive of AARP, formerly the American Association of Retired Persons.

The annual increase, even a modest one, is vital to beneficiaries because Social Security is the main source of income for eight out of 10 retirees, he said.

The average monthly benefit for retirees will rise from $903 to $922. For the average couple receiving benefits, the monthly check will jump from $1,492 to $1,523, an increase of $31. The average monthly benefit for disabled workers will rise from $844 to $862.

But for most older Americans, much of the increase will be wiped out by a 13.5 percent increase in Medicare premiums that also takes effect next year. Premiums will rise $7.90 a month to $66.60.

Medicare is very much on the minds of lawmakers in Congress with political attention turning to next year’s election.