Thrift institutions added to their mortgage securities holdings in 2005, although at a slower pace than the growth rate in the overall market, according to a new analysis by Inside MBS & ABS. Institutions regulated by the Office of Thrift Supervision reported MBS holdings of $172.56 billion as of the end of last year, an increase of 10.3 percent from the same point in 2004. That was still well below the MBS investments of OTS [Two data tables included]