NELP’s findings come at a time when income inequality and the failure of many workers to gain ground during the recovery are coming to the political fore. Candidates from both parties have sought to address the worries of middle-income Americans, while trying not to be too closely identified with Wall Street and other symbols of corporate America.

The past year has been the best for the job market since the end of the recession. Employers have added, on average, 243,000 people to their payrolls each month. That would normally constitute a “hot” job market, said Torsten Slok, chief international economist for Deutsche Bank Securities in New York.

“When you see all those jobs being added per month, you think, ‘Come on, how can this be bad?,’ ” Mr. Slok said. “But there has been a lot of pain and suffering, and people have been losing their skills or have not been able to re-skill.”

The roots of wage stagnation are deep, according to Mr. Slok.

Some of it is linked to what he calls the “glacial changes” wrought by macroeconomic forces like automation, demographics and globalization.

Other factors are specific to the American economy, including the real estate boom and bust, consumer debt levels and continuing slack in the labor market because of relatively low demand compared with the still-large numbers of people who are looking for work or would return to the labor force if they had a better chance of finding a worthwhile job.

For Ms. Almodovar, 36, acquiring new credentials and skills is a big obstacle.

When she talked with her employer’s human resources department about how to increase her long-frozen salary, their advice was to go back to school. Although Ms. Almodovar took the G.E.D. test and earned the equivalent of a high school diploma in her late 20s, taking classes would be a tough proposition now.

“I’m living with roommates, and if I don’t go to work, I don’t get paid,” she said. “Even one day makes a big difference.”