The estimated price tag of providing future health care benefits for workers who retire from Erie County government has dropped, but the county expects its annual costs for that insurance to rise over the next decade as more employees retire.

The latest estimate for the future cost of providing retirees health care benefits was $789.8 million as of Jan. 1, 2012, down $187.8 million from two years before that, according to a recent report prepared for Erie County. Actuaries attributed the decrease to several factors, including reductions in the number of workers and new union contracts for some employees that will require them to pay a portion of their health care costs in retirement.

The report, prepared by Harbridge Consulting Group, estimated that the amount the county will pay each year for retiree health insurance will grow from $20.5 million in 2012 to $40.2 million by 2022. The county attributed that growth to the number of retirements expected over the next decade “due to the advanced age” of the county’s workforce.

The county is required to report the actuarial present value of future benefits in its annual financial statements.