Nearly half of all mortgage borrowers did not refinance their home loan during the period between 2009 and 2012, when mortgage interest rates declined steadily, according to a Fannie Mae survey. The government-sponsored enterprise found that 40 percent to 50 percent of borrowers, for some reason, did not take advantage of low interest rates to reduce their monthly mortgage payments through refinancing. To try to get at why borrowers don’t refinance when the opportunity seems ripe, Fannie economist ...