JAMES TARANTO: ObamaCare’s Sex Problem: Too many women is another sign of adverse selection.

It can’t be stressed enough that the real story is almost certainly far worse than the age distribution would suggest. The reason the age distribution is important is that younger people tend to be healthier, meaning that they consume less medical service and are cheaper to insure. But some young people are sick too, and if they are the ones buying ObamaCare policies, that aggravates selection despite their tender years. But while this problem can be identified and anticipated, there is no way to estimate its magnitude. Insurance companies no longer ask about pre-existing conditions. . . .

Which brings us to a little-noted ObamaCare statistic that is also a sign of adverse selection: the sex ratio.

One of the selling points of ObamaCare was that it was a feminist triumph. “Being a woman is no longer a pre-existing condition,” read the lead sentence of a March 2010 news story in the New York Times, whose author, Denise Grady, then explained: “That’s the new mantra, repeated triumphantly by House Speaker Nancy Pelosi, Senator Barbara A. Mikulski and other advocates for women’s health. But what does it mean?”

What it means, in Grady’s words, is that “the new health care law forbids sex discrimination in health insurance.” Just as no one can be denied insurance or charged more because of a pre-existing condition, a woman and a man of the same age must be charged the same premium, and their policies must cover the same conditions–including maternity care for unmarried men (and women past childbearing age).

What it also means, however, is that women, like persons with pre-existing conditions, are more expensive to insure. The ban on what is called “gender rating” drives men’s premiums up as well as women’s down. (That doesn’t mean, by the way, that women pay less under ObamaCare than before. It may be that premiums rise for both sexes but the increase is steeper for men.) It means, further, that if ObamaCare enrollees are disproportionately female–just as if they are disproportionately older–premiums will tend to go up for everybody. And lo and behold, they are: The Department of Health and Human Services reports that of the 2.2 million people who have “selected a Marketplace plan,” 54% are female.

Sounds like more work for my Foundation For Gender Equity In Health Care. Or as has been said: “Although women tend to love the notion of government control more than men do, it is women who will be told they’ll have to cut back. On treatments. And years. You know we’ve been taking more than our share.”