Large tech companies are among some of the biggest spenders. Google’s parent, Alphabet, nearly tripled its first-quarter capital spending to $7.3 billion on real estate and computing capacity and data centers. Amazon increased investment by more than 40 percent to more than $3 billion as it builds out its network of fulfillment centers.

But with roughly a quarter of the companies in the S.&P. 500 having reported first-quarter results, their spending on buybacks is even higher, up 43 percent from the first quarter of 2017, to $43 billion, according to data from Howard Silverblatt, an analyst at S&P Dow Jones Indices.

Traditionally when companies have more cash than they think they can invest productively, they return it to shareholders either by paying them cash dividends or by going into the market and repurchasing shares. Those buybacks tend to push the price of a stock up, making shareholders wealthier, at least on paper.

Republicans, and some Democratic economists, say this can help the economy, if those shareholders sell their stock and then use their profits to make other investments. But critics argue that buybacks disproportionately benefit the wealthy — the richest 10 percent of Americans own 84 percent of all stock — and executives who are often compensated with shares.

Boeing said it had bought back $3 billion worth of its stock in the first quarter. (It expects to buy $15 billion over the next two years.) Facebook expanded its plans to buy back its shares to the tune of $9 billion. the appliance maker Whirlpool said it would sell its Brazilian refrigerator compressor business for roughly $1 billion, and then use that money to buy its own shares. The railroad operator CSX said it had bought back more than $800 million in shares in the first quarter, as part of plans to buy $5 billion in shares by the first quarter of next year.

As they anticipated a windfall from tax cuts, the nation’s banks increased their pace of buybacks by more than 50 percent last year, to $77.5 billion from $51 billion in 2016, according to data compiled by S&P Global Market Intelligence. The 10 largest banks, led by JP Morgan Chase and Citigroup, accounted for 70 percent of those buybacks.