http://blogs.wsj.com/washwire/2016/06/22/will-medicare-premium-increases-be-an-issue-in-november/

Buried in the Medicare trustees report released Wednesday are a few lines that could cause political controversy. “In 2017 there may be a substantial increase in the Part B premium rate for some beneficiaries,” the actuaries write—which means seniors will find out about increases shortly before Election Day.

Higher-than-expected Medicare spending in 2014 and 2015 set the stage for a large premium adjustment in 2016. But, notably, the absence of inflation thanks to the drop in energy prices last year meant that seniors receiving Social Security benefits did not receive an annual cost-of-living adjustment.

The Medicare statute has a “hold harmless” provision that prevents Part B premiums from rising by more than the amount of a Social Security cost-of-living adjustment. For most beneficiaries, the provision meant that in 2016, they received no such adjustment—but also did not pay a higher Part B premium. However, nearly one-third of beneficiaries—new Medicare enrollees, “dual eligibles” enrolled in both Medicare and Medicaid (in places where state Medicaid programs pay the Medicare Part B premium), and wealthy seniors subject to Medicare means-testing—do not qualify for the provision.

The New York Times noted last fall that the hold-harmless provision, by protecting most beneficiaries, exposed some to higher increases: “If premiums are frozen for 70 percent of beneficiaries, premiums for the other 30 percent must be raised more to cover the expected increase in overall Medicare costs. In other words … the higher Medicare costs must be spread across a smaller group of people.”