Savings institutions let their holdings in mortgage-related securities drain down slightly during the second quarter while continuing to shift more of their MBS investments into non-agency securities. Institutions regulated by the Office of Thrift Supervision reported $174.77 billion of mortgage securities in their portfolios at the end of June, down 0.9 percent from the previous quarter. Compared to a year ago, however, the MBS holdings of these institutions were up 10.0 percent... [Includes three data charts.]