NEW YORK (AP) — Flush with savings from lower tax bills and profits from a growing economy, big U.S. companies are spending a record amount buying back their own stock.

Stock repurchases hit $189.1 billion in the first quarter for the S&P 500, according to preliminary results from S&P Dow Jones Indices. That tops the prior record of $171.9 billion set during the summer of 2007, just before the Great Recession struck.

The robust buying of their own shares continues a yearslong trend where companies have returned more and more cash to their investors through buybacks and dividends. S&P 500 companies returned a total of $1 trillion to their shareholders in the 12 months through March, the first time they've passed that threshold.

Apple, Cisco Systems and other technology giants helped lead the way. Apple has traditionally been one of the biggest repurchasers of its own stock, and it set a record in the first quarter by spending roughly $23 billion.

By buying their own stock, companies can limit the number of their shares available in the market, which in turn allows remaining shareholders to lay claim to a bigger proportion of profits. Critics, though, don't like it when companies pay too high a price to repurchase their own shares, and the S&P 500 has quadrupled in value since hitting bottom in early 2009.

Some critics have also been pushing companies to spend more on investments and higher wages for workers, which would spur more economic activity, rather than returning it to shareholders. That has been happening more slowly than many had hoped, but things may be changing now that the unemployment rate is at an 18-year low.

"You saw a lot of money in the last several years go to stock buybacks and dividends, but with the unemployment market being as tight as it is, companies have to make investments to get more productive," said Ann Miletti, a portfolio manager at Wells Fargo Asset Management.

Miletti expects companies to spend more on software and other products to get more efficient, which would lead to bigger profits for technology and industrial companies.

More than a third of small businesses say it's a good time to expand, according to a survey by the National Federation of Independent Business. Wages have been trending a bit higher, meanwhile, even though they have not kept pace with corporate profits. Average hourly pay in the United States rose 2.7 percent in May from a year earlier.

While stock buybacks are getting bigger, they aren't happening uniformly across corporate America. They've become increasingly top heavy instead, and just 20 companies accounted for nearly half of all the S&P 500's repurchases during the first quarter, at 49.5 percent. That's a significantly higher percentage than in the last 10 years, when the top 20 purchasers accounted for an average of 41.5 percent of the index's total.

Don't expect companies to get less generous with their shareholders, at least anytime soon. Companies are raking in bigger profits after Congress overhauled the tax code by cutting rates for corporations and encouraging businesses to bring back cash that was parked overseas. Earnings per share for the S&P 500 rose 23 percent in the first quarter, and analysts expect overall growth of roughly 22 percent for the full year, according to S&P Global Market Intelligence.

"For the remainder of 2018, expectations are high for record corporate expenditures in both buybacks and dividends," said Howard Silverblatt, senior index analyst at S&P Dow Jones Indices.