Share buybacks hit their highest level in history last year, according to new data.

The total value of share repurchases by companies surged to a record $806.4 billion in 2018, up 55 percent from a year earlier, according to new data from S&P Dow Jones Indices. The record was more than 36 percent higher than the previous high watermark hit in 2007.

The buyback total is bigger than the market capitalization of all but four companies in the , eclipsing the size of top constituents like Facebook, Exxon Mobil and Berkshire Hathaway.

It's a common practice by publicly traded companies. Buying their own stock decreases the amount of outstanding shares in the market. Fewer shares out there means the remaining ones are worth more. It boosts earnings per share and is often used as an alternative to dividends. Critics say the move enriches stock-owning executives and increases income inequality.

The practice has come under scrutiny from some Washington lawmakers who say U.S. companies aren't spending the windfall from 2017 tax cuts to create jobs. These latest numbers will likely add to that debate. Earlier this year, Sens. Chuck Schumer, D-N.Y., and Bernie Sanders, I-Vt., said they would introduce a bill that seeks to put preconditions on companies that want to buy their own stock, including that they pay workers at least $15 an hour and provide other benefits. The senators wrote that the practice fuels a "pervasive corporate ethos" and adds to the worst level of income inequality in decades.

In a tweet, former Goldman Sachs CEO Lloyd Blankfein challenged that premise and said "the money doesn't vanish."

"It gets reinvested in higher growth businesses that boost the economy and jobs," he added. "Is that bad?"

Sanders, who is seeking the Democratic presidential nomination, responded that it doesn't vanish — "it increases the wealth of billionaires like him," referring to Blankfein.

Share repurchases have hit records for the past four consecutive quarters, according to the S&P Dow Jones data. Buybacks in the fourth quarter saw a 63 percent year-over-year jump to a record $223 billion. The record came as stock prices declined an average 5.3 percent that quarter, which let companies "buy even more shares for their dollars and reduce share count more efficiently," said Howard Silverblatt, senior index analyst at S&P Dow Jones Indices.

"Companies continued to spend more of their tax savings on these share repurchases as they boosted earnings through significantly reduced share counts," Silverblatt said in a press release.

Apple was the biggest spender when it came to buybacks. Last year, the iPhone maker spent $74.2 billion buying back its own shares — up from a total $34.4 billion in 2017. In the fourth quarter Apple poured $10.1 billion on buybacks, lower than the $19.4 billion it spent in the third quarter. It has now spent more than a quarter of a trillion dollars — $260.4 billion to be exact —over a 10-year period to buy back its own shares.

Oracle was the second largest buyer, followed by Wells Fargo, Microsoft and Merck.

But all sectors weren't spending equally. Information Technology buybacks in the quarter dropped to $61.3 billion compared with $82.3 billion a year earlier. Health-care buybacks more than doubled from the prior quarter.