The Republican tax reform package that was supposed to raise wages and spur hiring has instead funded a record stock buyback and dividend spree, benefiting investors and company executives over workers.

President Donald Trump signed the bill in December last year, saying the corporate tax cut would make it favorable for companies to bring back into the U.S. cash stashed in foreign operations.

"More than 70 percent of this [tax cut] will be returned to workers," said White House Press Secretary Sarah Huckabee Sanders at a January press conference after the bill came into effect.

However, companies have instead used the extra cash to spend billions of dollars buying back their own stock, boosting the value of shares held by investors. Buybacks reduce the number of shares on the market, immediately increasing the value of the shares that investors already hold.

Over the past year, S&P 500 companies have given their shareholders a record $1 trillion in the form of buybacks and dividends, led by Apple, Cisco Systems, and other technology giants.

Stock repurchases hit nearly $190 billion in the first quarter for the S&P 500, according to preliminary results from S&P Dow Jones Indices. The last time that record was set was just before the Great Recession, when companies bought up almost $172 billion of buybacks.

Compounding the issue is a recent study by the Office of SEC Commissioner Robert Jackson that found that a stock buyback announcement often leads to a short-term stock price pop, which corporate insiders use to cash out their shares.

"I think it’s high time the SEC reexamine its outdated buybacks rules,” said Rob Jackson, a commissioner at the agency.

Labor market expert Harry Holzer, a professor of public policy at Georgetown, told NBC News that he and his colleagues aren't surprised that the corporate tax cut's main beneficiaries haven't been workers.

"Productivity has been lousy in the U.S. since the dotcom boom ended, but companies have seemed to not need high productivity to have high profits, so they don't have incentive to invest in their workers or in capital," he said. "Throwing more money at them to lower corporate taxes is not something that will solve that problem."

“Repatriating cash from overseas or a windfall from lower tax bills has given many companies a surge of capital to put to work," Greg McBride, chief financial analyst for Bankrate.com, told NBC News. "There is little argument that wage growth has been the most sluggish aspect of the economy recovery.”

Some companies did use part of the tax cut to give their employees a one-time cash bonus, allowing them to benefit workers without raising the company's fixed costs. However, employees pay a higher tax on bonuses as supplemental income.

Average hourly pay has risen 2.7 percent in May from a year ago, but it's not as fast as the surge in corporate profits.

One solution might be to access the $2 trillion in excess reserves currently in the banking system, suggested Louis Hyman, an assistant professor at Cornell University's School of Industrial and Labor Relations, in an email.

"Instead of focusing on tax cuts, we should be focused on ways to get that capital invested in growth industries that employ ordinary Americans," said Hyman.