Finally, I will suggest the real test of whether a health-insurance program is stable is whether the consumers for whom it is intended believe that it provides them with value. Here is a chart of the take-up rate on the federal exchanges under the Affordable Care Act; excluding the “Over 400%” category, all of these individuals are eligible for subsidies. This chart represents data from last year, but with only a 4 percent reduction in those purchasing on the exchanges between 2016 and 2017, it should remain a fair indication of consumer approval of the program.

The health-insurance industry has long considered a 75 percent take-up rate to be the gold standard in evaluating whether an insurance pool is stable — i.e., whether there are enough healthy people signed up to pay the claims of the sick. While the exchanges appear to have achieved this for the lowest-income consumers — those who get the biggest premium subsidies and also have their out-of-pocket costs subsidized — only 17 percent of those making 301 to 400 percent of the poverty level have signed up.