JAMES TARANTO: California Dreamin’: ObamaCare’s bogus success story.

A representative sample of young people will be healthy and likely to stay that way for some time. But there is no reason to expect that the self-selected sample of young people who’ve undertaken the effort and expense of signing up for ObamaCare is representative. Sick people of any age have the greatest incentive to sign up. And the smaller the sample, the likelier it is to be skewed by selection bias.

Note that the total October enrollment of 30,830 comes to fewer than 1,000 a day, an order of magnitude smaller than the current pace of 10,000 a day claimed by Krugman. That, however, turns out not to be an apples-to-apples comparison. The 10,000-a-day figure, Covered California explains, is for “completed applications,” not actual enrollments, which totaled just 79,891 between Oct. 1 and Nov. 19. (A partial explanation for the disparity: Covered California estimates that 39% of applicants will be enrolled in Medi-Cal, so that their coverage will be completely at taxpayer expense.)

It remains to be seen whether even October’s less-impressive-than-advertised age distribution will hold up into November and beyond.

Read the whole thing. Say, did you know that Paul Krugman used to work as an Enron Adviser?