Subservicing shops increased their portfolios to $1.50 trillion during the third quarter, a 6.4 percent sequential gain, as mortgage originators continued to rely on such specialty vendors, according to exclusive survey figures compiled by Inside Mortgage Finance. Compared to a year ago, subservicing volume was up an impressive 28.2 percent. At Sept. 30, roughly 15.8 percent of all outstanding residential mortgages were being processed...[Includes one data table]