Mortgage refinance application volume skyrocketed 37% in the past week, according to the Mortgage Bankers Association’s seasonally adjusted index, in response to the lowest interest rates in almost three years. The national average on a 30-year fixed-rate conforming loan fell to 3.93% last week, down from 4.01% the week before. Borrowers rushed to take advantage of those low rates, pushing refinancing volume 196% higher than a year ago. Mortgage applications to buy homes did not move nearly as much, increasing just 2% for the week.