Fitch Ratings has updated its criteria for analyzing non-agency MBS for potential rating changes as well as criteria for determining whether cash flows from underlying residential mortgages are adequate to make payments on the rated non-agency MBS. Under the latest change to its surveillance process for non-agency MBS, Fitch said it will consider loan concentration risk as part of its surveillance analysis of pools that have a small number of mortgages remaining and lack certain structural features, such as sequential payment distribution or a subordination floor. Fitch’s latest criteria change will address ...