Rising premiums have priced some people who do not qualify for subsidies out of the Obamacare market, and there is some early evidence that more people who would have to pay full price for a plan are buying the so-called short-term plans instead. (But those plans aren’t available to people with pre-existing conditions.) Those shoppers tend not to be in the Obamacare market anyway.

People are signing up for Medicaid instead

The state with the biggest enrollment decline is Virginia. In that case, the drop can be explained by the state’s recent expansion of its Medicaid program, an option the Affordable Care Act encourages by committing the federal government to pay at least 90 percent of the expansion costs. By expanding Medicaid, Virginia made free government insurance available to low-income residents who had previously been buying coverage in the marketplace. Now, many appear to be switching to that.

Other states that have also expanded Medicaid have shown similar patterns of declining enrollment in the number of people signing up for Obamacare. But at the same time, they showed overall reductions in their number of uninsured residents, which is the ultimate goal of the law.

More people have jobs

As the unemployment rate drops, more Americans may be getting health insurance coverage from work. That too is a factor that could be driving down enrollment in Obamacare plans. Because unemployment has been falling since the Obamacare coverage first became available, it’s probably not a huge factor, but a tighter labor market could be reducing the overall number of people who need coverage.

For some people, the plans are less affordable

Prices always matter, and the prices people pay for Obamacare plans can be very different from the sticker price.

Last year, the sticker price for plans increased substantially. But for customers who qualified for subsidies, the prices they paid themselves actually went down. Many were delighted to find they did not have to pay anything for coverage.

This year, the sticker price of plans has declined slightly in many parts of the country. But for those people who get subsidies, typically about 85 percent of the market, prices may be going up a little in those places — and people may not be able to find a free plan this year.