Many Americans — especially women — are working more hours than they did three decades ago. But they’re not seeing a corresponding growth in wages.

A new analysis from the left-leaning Economic Policy Institute compared wages and hours from 1979 and 2015 to show that most workers saw increases in the amount of time they had to work to make the same amount of money.

“People are working more of the year,” Valerie Wilson, director at EPI’s Program on Race, Ethnicity, and the Economy, said. “Because we haven’t seen an increase in pay, people are having to work more to sustain their standard of living.”

This is particularly disconcerting news for workers in lower- to middle-income groups, who haven’t seen much of a raise in the past three decades but are working many more hours. (The median wage for all workers in 1979 was $16.36, compared with $17.33 in 2015, after adjusting for inflation.) That means, for example, a black woman in the middle-income group is logging an average of 279 more hours in 2015 than she would have in 1979. And if she’s part of the lowest-paid bracket, she’s working an extra 349 hours.

Collectively, the most dramatic increases in annual hours come from working women, going hand in hand with rising labor force participation rates, growing from 50.9 percent in 1979 to 56.7 percent in 2015. There is not only a higher share of women working today than in 1979 but also more women working full time, Wilson said.

The biggest shift in working hours was among the lowest-paid black women, who worked 30.1 percent more hours in 2015 than they did in 1979. Low-income white women saw a 27.6 percent increase, with 300 more work hours a year.

High-income black women, though, did not experience a marked increase in their work hours — only 6.2 percent — while highly paid white women, with a 21 percent increase, did.

“Black women didn’t seem to look like other groups in terms of the increases at the top and the bottom,” Wilson said. She posits that as more women moved into better-paying jobs, they worked longer hours commensurate with the work. But black women “haven’t seen that same level of ascension into those higher-paying, professional-type jobs over time,” she said.

Though the increases in men’s annual hours are less striking — men started with higher hours a year at the beginning of the period studied, so there’s naturally less room to increase — they also saw uneven distribution in annual work hours. Black men saw growth in top-, mid-, and low-wage jobs, but not so much in upper-middle or lower-middle jobs. White men saw a greater rise in hours in the highest-paying jobs, but not so much in lesser-earning jobs.

“I think that has a lot to do with the kinds of jobs that are available — mid-wage, middle-class jobs,” Wilson said. To the extent that increased demand for jobs would result in more working hours, “that hasn't been happening as much for men.”