Health insurance premiums paid by federal employees and retirees will increase 6.1 percent on average in 2018, the Office of Personnel Management (OPM) announced Wednesday.

Open season, when individuals can shop around and choose health insurance plans, runs from Nov. 13 through Dec. 11 for the Federal Employees Health Benefits Program. It is the nation’s largest employer-sponsored health insurance program, covering 8.3 million people.

The nearly two-thirds of enrollees covered by a Blue Cross/Blue Shield plan will pay $7.17 more per biweekly pay period next year than last year for self-only coverage; $17.04 more for self plus one other person and $17.72 for self and family coverage.

For enrollees with other health insurance companies, their premiums in those categories will increase by an average of $5.57, $12.55 and $12.17.

OPM said it “encouraged all insurance carriers to thoroughly evaluate their health plan options to find ways to improve affordability, reduce costs, and improve the quality of care and the health of the enrolled population. Negotiations were geared to keep premium increases as low as possible while minimizing changes in out-of-pocket costs, such as for deductibles, co-pays, and coinsurance.”

Average premiums for vision plan coverage will drop by 0.48 percent, while the cost of dental plans will rise by 1.26 percent.

“Open Season is important because these health benefits can help Federal employees care for themselves and their families,” OPM Acting Director Kathleen McGettigan said in a statement. “I urge Federal employees and retirees to carefully review their healthcare needs and to choose wisely among the plans and enrollment options available to them during this enrollment period.”

The government’s share of the premiums, which is determined by a statutory formula, will increase an average of 3.2 percent. The average overall increase, including the employer and employee share, will rise by 4 percent in 2018, compared to 4.4 percent last year.