Still, the core of Zuckerman’s argument stands. This recovery, compared to its post-World War II predecessors, has been exceptionally weak. The number of part-time workers who would like full-time jobs (defined by the Bureau of Labor Statistics as 35 hours a week or more) has dropped very slowly. In May 2009, it peaked at 9.1 million; as of last month, it was 8.2 million. Moreover, the level was (BEG ITAL)almost twice as high as before the recession(END ITAL) — 4.2 million in December 2006. As Zuckerman argues, this suggests many companies are quietly shifting employment practices.

Firms seek to minimize fixed labor costs by using contractors, “temps” and part-timers. Obamacare intensifies the pressures, because the incentives against hiring full-time workers are so obvious. A survey by the New York Federal Reserve of manufacturers in the state found that 6.5 percent had already refrained from hiring or had fired workers to stay below the 50-worker threshold; 5.4 percent said they had substituted some part-time for full-time workers. (These firms apparently represented a large share of the companies subject to the threshold, because most firms had more than 50 workers. The average firm employed 218.) A survey by the Philadelphia Federal Reserve produced a similar response.

Up to a point, part-time jobs reflect the flexibility of the U.S. economy — but we are well beyond that point. They increasingly signify weakness.