WASHINGTON — Millions of Social Security recipients and federal retirees will get only tiny increases in benefits next year, the fifth year in a row that older Americans will have to settle for historically low raises.

There was no increase this year. Next year’s benefit hike will be small because inflation is low, driven in part by lower fuel prices. The cost-of-living adjustment, or COLA, affects more than 70 million people — about one in five Americans.

The federal government is scheduled to announce the COLA, today. By law, the adjustment is based on a government measure of consumer prices. Preliminary numbers suggest a COLA of less than 1 percent, according to analyses by experts.

The average monthly Social Security payment is $1,238. That adds up to a monthly increase of maybe $3 or $4 a month.

More bad news: Medicare Part B premiums, which are usually deducted from Social Security payments, are expected to increase next year to the point in which they will probably wipe out the entire COLA.

By law, the dollar increase in Medicare’s Part B premium cannot exceed a beneficiary’s cost-of-living raise. That’s known as the “hold harmless” provision, and it protects the majority of Medicare recipients.

But another federal law says that the Part B premium must raise enough money to cover one-fourth of expected spending on doctors’ services. That means that a minority of beneficiaries, including new enrollees and higher-income people, have to shoulder the full increase. Their premiums would jump.

Since 2008, the COLA has been above 2 percent only once, in 2011. It’s been zero three times.