Amid the worst start for stocks ever, one long-time buyer is standing firm: U.S. companies. Whether that's reason for optimism is debatable.

American corporations repurchased more of their own shares in the first four weeks of the year than they did in the same period of 2015, according to Bank of America Corp. Goldman Sachs Group Inc. told clients this week that buybacks are accounting for nearly 20 percent of trading volume, according to two people who saw the note.

The data is subject to differing interpretations. While bulls will be glad to learn companies remain a reliable source of demand during one of the most volatile stretches in seven years, they may be less happy with the results. Almost $3 trillion has been erased from American equity prices in 2016 as concerns ranging from China to the Federal Reserve spurred one of the broadest retreats from risk since the financial crisis.