While the headlines focused on a decline in the official U.S. unemployment rate from 7.9 percent to 7.7 percent, Barron’s “Economic Beat” columnist Gene Epstein digs deeper into the numbers to find a persistent employment problem masked by the official unemployment rate.

In order to qualify as officially unemployed, jobless respondents must tell the BLS interviewer that they actually want a job, and that they have made some minimal effort to look for work over the previous four weeks. Since that can simply include calling a friend or relative about potential employment, or sending out a single résumé, qualifying for the official job count is easy. But as a check on its official measure, which it calls U-3, the agency keeps three broader gauges, U-4 through U-6. U-6 includes involuntary part-timers who are searching for full-time positions. And as I’ve reported before, U-6 has been saying that labor underutilization is a worse problem than U-3 implies.

The number of involuntary part-timers in February came to nearly eight million, up from its recent low of 7.7 million in March of last year. It’s the key reason why U-3 reached a cyclical low, while U-6 has not.

Why has the number of involuntary part-timers refused to decline? One explanation: the perverse incentives resulting from Obamacare, which requires that employers with at least 50 workers on their payrolls buy health insurance for those who work 30 hours or more. There is therefore an incentive to keep workers on part-time status, even if they want full-time work. If that is what’s happening, this form of underemployment might persist long past the point when it should be self-correcting.

Thanks again, Mr. President.