The number of homeowners who could save by refinancing more than halved from the start of the year to 5.9 million, according to Black Knight. Black Knight considers refinancing candidates as 30-year mortgage holders with a loan-to-value ratio of up to 80%, a credit score of 720 or higher, and the potential to reduce their current first lien by at least 0.75% .

The average 30-year fixed-rate mortgage rose about 50 basis points in the first few weeks of the year.