Social Security recipients will be getting a 2 percent cost-of-living adjustment (COLA) in 2018, the biggest increase since 2012.

This year, 42 million retirees are receiving Social Security payments averaging $1,377 a month, or about $16,524 a year. With the 2018 COLA, payments will average $1,404 a month, or $16,848 a year.

The 2018 COLA could be crimped by higher Medicare Part B premiums. The standard premium is now about $134 a month, but many participants pay about $109 a month if they have the fee deducted from monthly benefit payments. A “hold harmless” provision in federal law prohibits Medicare from raising a person’s Part B premiums if it reduces their Social Security benefits. For the past two years, most Medicare beneficiaries have been held harmless because, without a significant COLA, increasing their premiums would have resulted in lower Social Security benefits.