Mortgage rates have been historically low for several years, but a surprising number of borrowers are still not taking advantage even though rates fell again at the start of this year. How many? Close to 7 million.

After the Federal Reserve raised its target interest rate in early December, the common expectation was that mortgage rates would rise. Refinances had already dropped by nearly a third throughout 2015, as rates inched up in anticipation of the Fed's move.