Workers sort papers on an assembly line at a recycling plant. (iStockphoto)

The economic status of white men without a college education is bleaker now than a generation ago, a new study shows.

Although the working-class and college-educated start their adult lives with roughly similar incomes, the earnings for those with college educations begin to soar soon after they enter the workforce, while earnings for those with only a high school education leveled off much earlier, according to a report released Wednesday by Sentier Research, a firm led by former census officials, that analyzed outcomes for white men from 1996 to 2014.

The report also found that the gap in fortunes between the ­college-educated and those with high school degrees or the ­equivalent has widened dramatically in the past 20 years. Adjusted for inflation, white working-class men earned more from 1978 to 1996 than they did from 1996 to 2014, while earnings for ­college graduates rose during that period.

The study focused heavily on white working-class men because their perceived fall in economic stature has been a focus of recent campaign-related news reports, said Gordon Green, one of the study’s authors.

“Everybody’s talking about this group and how badly they’ve suffered, but there really hasn’t been any hard data till now,” Green said, adding that the decline in fortunes has been long underway. “We’ve been losing industrial jobs for several decades and many of the ­working-class people were in these kind of jobs, and once those jobs went overseas they could not get comparable pay. . . . The people who were working in those jobs didn’t have the training for the higher technology, for the way jobs evolved.”

Working-class white men have fueled Donald Trump’s support in both the primary and ­general-election campaigns. A national Washington Post-ABC News poll before the first ­presidential debate found that among likely voters, white men without college degrees ­supported Trump over Hillary Clinton by a 76 percent to 17 percent margin, ­exceeding Mitt Romney’s 64 percent support among this group in 2012. That compares to an 11-percentage-point margin in Trump’s favor among white men with college degrees and a 12-point margin for Trump among white women without degrees. Clinton led Trump 25 points among white women with college graduates.

The Sentier study divided working-age white men into two-year cohorts and tracked their earnings over 18-year periods ending in 1996 and 2014. The analysis divided the total earnings in each group by their population size to include data from those who were not in the workforce at all, increasing the discrepancy between the two ­education groups.

Between 1996 and 2014, wages and salary income for those with a high school degree rose by only 19 percent ($32,677 to $38,803) during the first two decades of their careers, while it rose by 133 percent ($40,487 to $94,252) for college graduates.

“This puts an exclamation point on why today many in the white working class feel left out, and particularly men in their 40s and 50s,” said William Frey, a demographer at the Brookings Institution. “They’re doing worse than they even thought they might 20 years ago.”

But the sharpening divide highlighted in the study does not tell the whole story of what has happened to the workforce, said Gary Burtless, a labor economist at Brookings, noting that the numbers of people in each category have shifted. In recent years, the proportion of people attending college has grown while the proportion who never attended college has dwindled.

In 1978, 70 percent of Americans had a high school diploma or less and 16 percent had college degrees. By 1996, the gap had narrowed to 52 and 24, respectively, and today, 41 percent have a high school diploma or less and 33 percent have college degrees. The study did not look at people with some post-high-school education but no college degree, which includes more than a quarter of Americans.

Data analyzed by the Pew ­Research Center for The Post finds racial and ethnic minority groups have significantly lower earnings than whites. Among those without college degrees, the typical household income for whites was about $56,600 in 2014, compared with $47,900 for Asians, $38,800 for Hispanics and $35,900 for African ­Americans.

The shrinking group of non-college-educated Americans are the ones who were most likely to fall behind in the past 40 years, Burtless said, adding that earnings among nonwhite men have followed trends similar to those in the study.

While college graduates tend to have high employment rates throughout their life span, he said: “People with the least education have been the ones most likely to drop out of the workforce, stay out of the workforce, retire early, go on disability.”

And as more people attain college degrees, those who don’t have them are increasingly ­falling behind when competing for jobs.

“Those people are both a smaller minority in 2016, and they’re relatively more disadvantaged, given the fact that other people their age have attained more schooling,” Burtless said.