The 55-year-old Lewis, a visiting scholar at the SEC now, moves to his new position in June, the SEC said. As director of the Division of Risk, Strategy, and Financial Innovation, he will replace Henry Hu, who stepped down after about a year in that post.

"His two tours as a visiting academic fellow at the SEC give him important insights into the agency's inner workings and uniquely position him to fulfill my vision of the Division," SEC Chairman Mary Schapiro said. RiskFin, was created by the agency in 2009 to serve as its research facility.

"I think it's important to have an economist running RiskFin," Cynthia Glassman, an economist and former SEC commissioner, told Bloomberg News. She said that economists have analytical expertise that many lawyers lack.

Lewis, a 28-year veteran of academia, will study the economic impact of potential rules, which could serve well in the development of guidance under the Dodd-Frank Act's overhaul.

The agency had been without a chief economist since Jim Overdahl left in March 2010. Shortly before he resigned, the chief economist position was moved from directly reporting to the SEC chairman to working in the RiskFin division.