Companies have been feverishly putting the savings they reaped from the tax breaks passed in December into their investors' pockets this year.

Share buybacks in 2018 have averaged $4.8 billion a day, double the pace for the same period last year, according to market data firm TrimTabs. That comes following Congress's move to slash the corporate tax rate from the highest-in-the-world 35 percent to 21 percent.

The buyback announcements also have happened amid a volatile backdrop for the stock market, which briefly endured a correction in February — defined as a 10 percent drop — but have rebounded to near record highs in March. The share repurchases have helped keep the market afloat, as investors have pulled $23.5 billion out of funds that focus on U.S. stocks this year, according to Bank of America Merrill Lynch.

"The feverish buyback activity suggests companies plan to use a hefty chunk of the money they expect to save on taxes to buy back stock," David Santschi, director of liquidity research at TrimTabs, said in his weekly report.

"Share repurchases are arguably the most conservative things companies can do with their money other than pay down debt," he added. "Buy why pay down debt when central banks allow you to borrow for almost nothing on an after-tax basis?"

Tax-cut opponents feared that companies would use the windfall to benefit shareholders rather than grow through investments in capital and manpower. The most recent data suggest that the money is flowing in both directions.