Donald Trump can boast at least a little bit about the return of manufacturing jobs during his presidency. Employment in the sector is up by 125,000 since January. It's not exactly a boom, after all, we are still down by almost 1.3 million jobs from the pre-recession level and 4.8 million from where we were in 2000, but at least it is movement in a positive direction.

In an NYT Upshot piece, Neil Irwin sorts out the reasons for this modest uptick in manufacturing jobs. He points to a small increase in oil prices and a drop in the dollar, both of which are likely factors. (He also points to weak growth in government employment. I'm not sure how that matters here.)

However, Irwin left out what might be the most important reason for the increase in manufacturing jobs: weak productivity growth. According to the Bureau of Labor Statistics, output in manufacturing has increased at 2.0 percent annual rate in the first half of 2017. This would mean that if we had a modest 2.0 percent rate of increase in productivity in the sector (manufacturing productivity usually grows faster than the rest of the economy), we would have no need for more labor, and presumably no new jobs.

But now America is great again, manufacturing productivity has slowed to a crawl, increasing at just a 1.4 percent annual rate in the first half of the year. So, there we have it, extraordinarily weak productivity has translated into 125,000 new manufacturing jobs under President Trump.