Social Security and Supplemental Security Income benefits are expected to increase next year by the largest amount in more than 40 years, a new estimate suggests.

Benefits could rise 8.7% in 2023, according to a projection this week from The Senior Citizens League, a nonprofit that advocates for seniors.

That would be the biggest increase since 1981 when there was a 11.2% rise. It would also be substantially higher than the 5.9% increase at the start of this year.

The changes are due to an automatic cost-of-living adjustment, or COLA, that Social Security and SSI beneficiaries receive annually, which is intended to account for inflation.

“A COLA of 8.7% is extremely rare and would be the highest ever received by most Social Security beneficiaries alive today. There were only three other times since the start of automatic adjustments that it was higher,” said Mary Johnson, Social Security and Medicare policy analyst at The Senior Citizens League, referring to the COLAs between 1979 and 1981.

COLA is based on how third quarter figures from the government’s Consumer Price Index for Urban Wage Earners and Clerical Workers, or CPI-W, compare with those from the previous year.

The latest estimate from The Senior Citizens League comes after the U.S. Department of Labor’s Bureau of Labor Statistics released its CPI-W data for August earlier this week.

The official COLA announcement for 2023 from the Social Security Administration is expected in October.