The Securities and Exchange Commission banned Standard & Poor’s, the world’s largest credit rater, from a large part of the mortgage market for one year. SEC says the time out is because of ratings S&P issued in 2011 that regulators claim were “misleading.”

The suspension will bar S&P from rating securities backed by bundles of loans tied to such structures as shopping malls and office buildings. The ban is significant because investors typically require these kinds of bonds to be graded by two of the three ratings agencies, and now that S&P has been benched, the math is easy.

“So, who do they go to? They have to now, sort of go to Moody’s and Fitch,” says Amiyatosh Purnanandam, a University of Michigan finance professor. The long-term impact of the ban may extend well beyond a year because so much sensitive information is shared with ratings agencies. “Once you as a potential rater have giving all of this Fitch, you would be reluctant to switch to S&P, even after a year when S&P comes back into the game,” he says.

S&P can still issue ratings for corporate bonds. They can also service the residential and municipal bond markets. Moreover, some say the securities S&P is not allowed to rate were never really in its wheelhouse.

“It’s not like these companies are going to be doing more business now that S&P has dropped out,” says Dick Larkin, director of credit analysis for H.J. Sims.

In a statement, S&P said that it does not admit or deny any of the charges filed against it. The company also agreed to pay $77 million to the SEC, New York and Massachusetts to settle charges tied to its ratings of mortgage-backed securities.