When mortgage rates fall, many Americans go to one of their local mortgage companies to refinance their loan rate. However, many who could save thousands of dollars by refinancing their loan do not. In fact, a study by the National Bureau of Economic Research found that 20 percent of homes that could have profitably refinanced in December 2010 failed to do so, missing out on a median savings of $11,500 over the lifespan of their loans (or $160 on a monthly basis). That’s a lot of money that could have been saved. Here’s a look at what that $11,500 can do.