Mary Schapiro took the lead at the Securities and Exchange Commission last year, vowing to quickly pursue short-selling restrictions and other changes. More than a year later, the SEC has not established additional limits on short selling or made most of the other regulatory changes it had proposed. Ms. Schapiro defended the SEC's progress. "It can take more time than one might have thought at the outset," she said. "We have to understand the real-life implications of what we're doing, the unintended consequences. We need to digest all the comments and all the economic analysis. And that leads us down a path that sometimes isn't 100% predictable at the beginning."