The government overseer of Fannie Mae and Freddie Mac wants to help trim the footprint of the two government-sponsored enterprises by selling credit risk to private investors, but a top public policy analyst questions how effective such efforts will be in bringing private capital back to residential mortgage markets. “The basic business model of credit-risk insurance doesn’t just make sense,” said Karen Shaw Petrou, managing partner at Federal Financial Analytics, a think-tank in Washington, DC. “Because of the damage done in the run-up to the crisis, traditional insurers are at great risk of being...