First, there is the decline of the number of jobs in manufacturing and other industries that once paid less-skilled workers good wages, a result of technology and globalization. Second, there are changing norms around worker pay and the workplace — less union power, for example, a lower minimum wage when adjusted for inflation, and a culture in corporate America of cutting labor costs to the bone.

It would be dangerous to read too much into a relatively simple crunching of census data, but the Hamilton Project numbers offer some evidence for both.

First, there really is a shift away from the sectors where less-educated workers can earn a decent living. In 1990, 40 percent of the prime-age male workers without a high school diploma worked as operators and laborers, a number that declined to 34 percent in 2013. Jobs in food service, cleaning and groundskeeping nearly doubled in the same span, to 21 percent from 11 percent. But it wasn’t an even trade: Pay for operators and labors was $25,500 in 2013, compared with $20,400 for the food, cleaning and groundskeeping category.

You’re not imagining it. The jobs that are being created for less-educated workers really do pay less than the ones that are being lost. That suggests that globalization and technological change — the shifts that are making those machine operator jobs fewer and farther between — are a factor in depressed wages.

But the shift in occupational categories, the researchers found, accounts for only about a third of the decline in pay for men without a high school degree and one-sixth of the decline for those with a degree. A bigger effect is downward pressure on pay in jobs held by low-education workers across the board.

So not only did people shift from higher-paying fields to lower-paying ones, but inflation-adjusted pay also fell in all of those jobs. For example, production work — manufacturing, largely — was the highest-paying category for men without a high school diploma in 2013, paying them $28,000. But that sector was both smaller (29 percent of such workers, down from 31 percent) and paid less (down from $33,600) than it did in 1990.

The drop in pay across the board for low-education workers hints more at some of those factors around employers’ bargaining power and practices. Both factors could come into play, though. For example, perhaps a rise in automation and globalization is eliminating manufacturing jobs, and the people who once held those jobs are now competing for work as janitors and food preparers, and the additional supply is helping to depress wages in those fields.

“One thing that’s always bothered me about the political debate is people want to say either it’s globalization and technology, or it’s institutions,” said Ms. Kearney, who is director of the Hamilton Project and a professor at the University of Maryland. “But of course it’s both.”