Health Affairs attributes the rise in insurance costs largely to the health insurance tax, which was suspended in 2017 but went back into effect in 2018.

The spending increase came despite roughly 1 million fewer people with insurance coverage. The drop in coverage was driven largely by attempts by the Trump administration and Congress –– in both 2017 and 2018 –– to undermine the Affordable Care Act. Most significantly, the tax law enacted at the end of 2017 eliminated the ACA's individual insurance mandate.

Medicare spending grew at a much faster rate, 6.4 percent, to $750 billion. While enrollment growth was typical (2.6 percent), per-enrollee expenditures rose by 3.7 percent, compared to only 1.6 percent in 2017. The portion of Medicare spending on private plans increased by over 11 percent, and now accounts for 36 percent of overall spending in the program.

In contrast, Medicaid spending only grew by 3 percent, reaching $597 billion. Per-enrollee spending grew by 2 percent.

One bright spot for consumers was the relatively modest growth in spending on prescription drugs: 2.5 percent. In fact, prices for retail prescriptions declined 1 percent.

Hospital spending was up 4.5 percent and spending on physicians and clinical trials went up 4.1 percent.

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