While many would-be retirees who stay on the job do so because they enjoy the work and want to remain engaged, there are plenty more who wish they were able to ditch the 9-to-5 routine but are staying out of financial necessity to retain medical coverage.

And those are the very ones employers would like to say farewell to.

But the pre-Medicare retiree group, usually those who are younger than 65, face health care cost increases when they retire that average approximately double the increases that have to be paid by Medicare enrollees, according to research from Willis Towers Watson—hence their desire to keep working.

And even well-meaning employers who’d like to provide some help—even if only to get those reluctant older workers out of the office to make room for younger employees impatient to move up the ladder—find that cost presents a financial challenge.

However, that’s not the end of the story. According to the report, among respondent employers to Willis Towers Watson’s survey last year, 72 percent planned “moderate to significant” changes in pre-Medicare retirement health benefits through 2020.

Many of them indicated that they’re shifting Medicare-eligible retirees to private exchanges such as Willis Towers Watson’s OneExchange, Mercer’s Mercer Marketplace and Aon Hewitt’s Aon Retiree Health Exchange.

Negotiations with the insurers participating on the exchange allows employers to set the level of subsidy they wish to provide for coverage that retirees purchase.

But some employers, like Wesleyan University in Middletown, Connecticut, stick to the traditional method of offering a group health insurance plan for early retirees. They’ve done so for 25 years, with the university paying two thirds of the premium.

And Duke University goes the traditional route as well, offering retiree coverage in its group health plan; the retiree’s percentage of premium is calculated based on the “Rule of 75.”

The total of the retiree’s age and years of service must add up to 75, after which the university pays 60 percent of the individual premium and the retiree pays 40 percent. Duke also pays at least 50 percent of premiums for spouses and other dependents.