Mortgage rates were already in line with the lowest levels since December 18th by last Thursday. They dropped to the best levels since December 12th a day later. end of last week. 

When today's initial rate offerings came out, the average lender was unchanged from Friday, but as the day progressed, bonds improved and many lenders were able to offer a modest improvement. 

The result is that we can once again say that rates are the lowest since December 12th, even if most borrowers would see no difference in loan quotes from Friday.

The bond market (which underlies and dictates interest rate movement) was very calm today after early gains. Investors are waiting to see Friday's PCE inflation data before making any big moves in either direction, but there is also some smaller risk of volatility surrounding other events this week.  Honorable mentions include the Treasury auctions on each of the 2 following afternoons as well as Thursday morning's slate of economic data.