Mortgage banking and brokerage firms are about to start laying off production workers as refi applications continue to decline, but industry executives say the heaviest layoffs are unlikely to come until the end of summer. That’s when lenders begin closing mortgages that first entered the pipeline in May, when the application picture was brighter. According to figures compiled by the Bureau of Labor Statistics, the mortgage banking and brokerage sectors employed 293,800 full-time workers in May, compared to 295,500 in April, a loss of 1,700 positions. Compared to a year ago, employment is up 10 percent. The brokerage sector alone employed...