Mortgage banking remained highly profitable during the first quarter of 2013, but the hefty margins earned in secondary market activity declined and production volume tapered off, according to the Mortgage Bankers Association’s quarterly performance report. The average firm participating in the survey generated $3.65 million in pretax income during the first quarter, off 22.5 percent from the previous period, the MBA said. That was still well above the $2.33 million in average earnings for the ...