This kind of work is growing at the expense of more physically onerous labor. Mining and manufacturing—the two sectors most represented in Lordan and Pischke’s brawn category—were the only major industries to lose jobs in the last twelve months, a period when the economy added a net 2.4 million new workers. Together, M&M lost about 160,000 jobs in the last year. Education and health services, by comparison, added about 640,000 net new jobs.

In the summer of 2016, when all news seems to percolate through the filter of the presidential election, the labor economics of brawn takes on new meaning in the context of the Trump phenomenon. It feels like a microcosm of the contrast between the economy Obama, Clinton, and others point to—a historically steady recovery—and the economy that Trump describes—bleak, rusted, sundered by trade and technology.

On the one hand, the U.S. private sector is in the midst of its longest-ever continuous expansion, and the U.S. has recovered from the Great Recession faster than many rich countries in Europe. But national averages overlook the discrete experience of many cities that are lagging behind, particularly in areas that have lost the most manufacturing and mining work—the Brawn Belt of Appalachia and the Midwest. Cleveland's workforce is shrinking, Toledo lost 4 percent of its businesses between 2008 and 2012, and 61 percent of Detroit's adults aren't working.

Trump’s coalition is not purely a reflection of labor market changes. (Racially spiked attitudes toward immigration and trade seem to unite them more than any economic detail or policy.) But it is striking that Trump continues to perform strongest among the very demographic that has historically performed America’s brawny jobs: the marrow of the old-fashioned blue-collar workforce, men without a college degree, particularly white men. Down seven points in national polling, Trump still leads among white men without a college degree by an astonishing 40 points.

It’s well known among economists that not all is well in the male-dominated workforce. The share of non-working men in their prime working years, between 25-54, has doubled since the 1970s, and one-in-six prime-age men in America are either unemployed or not looking for work. This is a complicated trend, with disperse and tangled roots, including mass incarceration and disability insurance policy. But one likely contributor is that the job categories growing the fastest include work that have historically been done by women. “Women have always been dominant in occupations which score high on ‘people’ (e.g. teaching, nursing, and social work),” Lordan and Pischke write. Meanwhile “the ‘brawn’ factor” is associated with traditional blue-collar occupations that are in secular decline.

It was perhaps inevitable that the debrawnification of American work would trigger a national identity crisis, with unpredictable eruptions. "Some of the decline in work among young men is a mismatch between aspirations and identity," Lawrence Katz, a professor of economics at Harvard University, told me in 2014. "Taking a job as a health technician [or social worker, or nurse] has the connotation as a feminized job. The growth has been in jobs that have been considered women’s jobs—education, health, government.”