Social Security Benefit to Rise 4.7% : Pension: The annual cost-of-living adjustment will be the biggest in 7 1/2 years.

The nation’s 38.9 million Social Security beneficiaries can count on a 4.7% benefit increase in January that will boost the average retired worker’s pension by $25 a month, the government said today.

The annual cost-of-living adjustment, the biggest in 7 1/2 years, will increase the typical benefit check to $566 a month, the Social Security Administration said.

For someone who retires at age 65 in 1990, the maximum monthly benefit will be $975, up from $899 this year.

The raise, announced after the Labor Department released its consumer price report for September, mirrors the inflation rate for urban wage earners and clerical workers from the third quarter of 1988 through the same period this year.

“Social Security’s 39 million beneficiaries, including the elderly and disabled reliant upon fixed incomes, can rest assured their buying power will be maintained,” Social Security Commissioner Gwendolyn King said in a statement.

The increase will show up in checks delivered Jan. 3, representing benefits earned for December.

The government also announced today that the so-called wage base--the maximum amount of current workers’ earnings subject to the payroll tax that finances Social Security benefits--will rise from the current $48,000 to $50,400 next year.

Only about 10.4 million of the 130 million workers subject to the payroll tax had earnings that exceeded the wage base this year, the Social Security Administration said.

However, all workers and employers face higher payroll taxes next year, since the tax rate rises from 7.51% to 7.65%, an increase that was approved by Congress back in 1977.

The two changes--higher wage base and higher tax rate--mean that the maximum tax on employees will jump by $250.80, to $3,855.60, in 1990 for workers earning over $50,400. Employers match their workers’ contributions.

Next year’s benefits increase for retirees will be the biggest since a 7.4% raise in July, 1982, when high inflation rates translated into bigger cost-of-living adjustments. Benefits rose 4% in 1989.

The Social Security Administration gave the following examples of how the benefit increase will affect average monthly benefits.

--Older couple, both getting benefits: up $43 to $966.

--Widowed mother and two children: up $53 to $1,173.

--Older widow living alone: up $24 to $522.

--Disabled worker, spouse and children: up $44 to $975.

--All disabled workers: up $24 to $555.

Of the 38.9 million people receiving monthly Social Security benefits, 62% are retired workers, 7% are disabled workers and 31% are spouses or children of retired, disabled or deceased workers.

For the elderly and disabled, the increase in Social Security benefits will be partially offset by an extra $2 a month in Medicare premiums, which rise to $33.90 in 1990. The premiums are deducted directly from Social Security checks.

The nation’s 4.5 million recipients of Supplemental Security Income, a federal program that provides a minimum income floor for poor people who are aged, blind or disabled, also will receive a 4.7% benefit increase at year’s end.