Firms that specialize in subservicing home mortgages for others continued to post steady gains in the first quarter, according to a new tally from Inside Mortgage Finance. The nation’s 20 largest subservicers held $1.689 trillion of contracts at March 31, a 5.1 percent sequential gain and a hefty 24.1 percent improvement from the same period a year earlier. Also, roughly $1.877 trillion of the nation’s mortgages are...[Includes one data table]