Fitch Ratings will allow for differences in third-party due diligence practices when rating various types of residential MBS, granting concessions to risk-sharing transactions from the government-sponsored enterprises. The firm released revised master-rating criteria late last week. Among the changes compared with criteria that were released in October was an allowance for differences among non-agency MBS backed by recent originations, transactions related to the GSEs and non-agency MBS backed by seasoned loans. While most jumbo MBS issued in recent years have included third-party due diligence reviews of 100 percent of the loans in a deal, the GSEs’ much larger risk-sharing transactions have been...