For the last 46 years, the 30-year mortgage rate has been almost perfectly correlated with the yield on the 10-year Treasury, but not this year. From Dec. 29, 2016, through today, the 30-year mortgage rate fell 17 basis points to this week’s reading of 4.15 percent. In contrast, the 10-year Treasury yield began and ended the same period at 2.49 percent. A year ago at this time, the 30-year FRM averaged 3.65 percent.