"I think the challenge it illustrates is that it is going to be very hard to come up with a scenario where there is no impact on mortgage rates," Hornung said of the study. Researchers applied Fannie Mae's recent quarterly g-fee average of 67 basis points to 2023 Urban Institute data. "There are some levers that they could pull to try to either keep mortgage rates constant or potentially even give them a modest decrease," Sampson said. However, it could put the GSEs back in a situation that proved problematic in the past, Hornung said. "What led to the financial crisis in the first place was this really substantial risk that Fannie and Freddie were holding on their balance sheet in terms of MBS," Hornung said.