But this next sentence in her speech really got the attention of industry: “We also have to take a hard look at stock buybacks. Investors and regulators alike need more information about these transactions. Capital markets work best when information is promptly and widely available to all.”

She then offered what some think is her first salvo in the regulation of buybacks: “Other advanced economies — like the United Kingdom and Hong Kong — require companies to disclose stock buybacks within one day. But here in the United States, you can go an entire quarter without disclosing. So let’s change that.”

Mrs. Clinton raises an interesting point about the disclosure rule, one that, if changed, would most likely make it much tougher — or at least more expensive — for American companies to buy back shares. Indeed, international companies have done a lot less of it.

Her point tiptoes around a more explosive claim from Senator Elizabeth Warren and Senator Tammy Baldwin that buybacks might be a form of market manipulation. Both senators have urged the Securities and Exchange Commission to investigate the practice.

In discussing buybacks in an interview with The Boston Globe, Ms. Warren provided a bit of a history lesson: It wasn’t until 1982 that the S.E.C., under the chairmanship of the Reagan appointee John S. R. Shad, gave companies so-called safe harbor against charges of manipulation if they bought their stock in the open market under certain circumstances. (The provision is known as Rule 10b-18.)

“These buybacks were treated as stock manipulation for decades because that is exactly what they are,” Ms. Warren said. “The S.E.C. needs to recognize that.”

Indeed, it was that rule change that led to the surge in buybacks, which were considered shareholder friendly. And it’s considered tax efficient: Unlike a dividend, there is no tax to be immediately paid.