Freddie Mac released its weekly update on national mortgage rates on Thursday morning, showing an increase in the average price for fixed-rate mortgages and no change in adjustable-rate mortgages.

Both 30-year fixed-rate mortgages (FRMs) and 15-year FRMs got more expensive over the past seven days, rising six basis points apiece. 30-year FRMs now average 4.33% interest, and 15-year FRMs cost 3.39%. One year ago, 30-year FRMs cost 3.40%, and 15-years 2.61%.

Neither 5/1 adjustable-rate mortgages (ARMs) nor 1-year ARMs, however, changed in price at all. 5/1 ARMs cost 3.03%, just like a week ago, and 1-year ARMs are still 2.44%. A year ago, these rates were 2.58% and 2.62%, respectively.

The fact that existing-home sales declined 0.2% in March, while new-home sales fell 15% would ordinarily be expected to push mortgage interest rates down, rather than up. However, Freddie Mac vice president and chief economist Frank Nothaft  noted in a statement a possible connection between the unexpected rise in long-term fixed mortgage rates and an "uptick" in 10-year Treasury yields over the past week.