“One of the issues that concerns me is what we are seeing happening to working families all across this country,” Sanders said during a congressional hearing on the U.S. economy and budget outlook.

“The average worker in America has seen zero — zero — wage growth over the past year, after adjusting for inflation,” he said, citing the bureau's report.

According to the Bureau of Labor and Statistics, average weekly earnings increased by 0.9 percent from March 2017 to March 2018.

ADVERTISEMENT However, for roughly 80 percent of workers — those categorized in the report as production and nonsupervisory employees — the increase in average weekly earnings totaled only 0.3 percent over the last year. The boost came from a slight increase in the number of hours worked each week, a positive sign for underemployed workers.

But setting aside increased pay for additional time spent working, the report showed the amount earned per hour of work was flat. Most workers earned a price-adjusted $9.21 per hour in March — no different than the previous year.

The figures indicated that wage increases driving the top line numbers were concentrated among high earners.

That could be bad news for Republicans, who promised that their tax-reform bill would increase wages across the economy. The tax bill went into effect in January of this year.

A Congressional Budget Office economic study released on Monday also noted that wage increases were likely to to be concentrated at the top.

The study estimated that payroll taxes — taxes taken out of salaries to fund programs such as Social Security — would decline as a share of the economy, dipping from 6.1 percent of gross domestic product in 2017 to 5.8 percent in 2019, and inching their way back up to 6 percent over the course of a decade.

“The decline from 2017 to 2019 is caused in part by the expectation that wages and salaries will continue to grow faster for higher-earning taxpayers than for other taxpayers,” the report noted.

As a result, high-end earners are likely to surpass caps on payroll taxes, limiting their contributions to those funds.