by Calculated Risk on 2/25/2010 02:07:00 PM

First, the following graph is from the Atlanta Fed Financial Highlights, and shows the weekly Fed MBS purchases since January 2009:

Click on graph for larger image.

From the Atlanta Fed:

The Fed purchased a net total of $11 billion of agency-backed MBS through the week of February 17. This purchase brings its total purchases up to $1.199 trillion, and by the end of the first quarter of 2010 the Fed will have purchased $1.25 trillion (thus, it is 96% complete).

Freddie Mac report that mortgage rates increased last week. From Freddie Mac: Long-Term Rates Rise to Over 5 Percent for the First Time in Three Weeks

Freddie Mac today released the results of its Primary Mortgage Market Survey® (PMMS®) in which the 30-year fixed-rate mortgage (FRM) averaged 5.05 percent with an average 0.7 point for the week ending February 25, 2010, up from last week when it averaged 4.93 percent. Last year at this time, the 30-year FRM averaged 5.07 percent.
...
“Interest rates for 30-year fixed mortgages followed long-term bond yields higher and rose above 5 percent this week amid a mixed set of economic data reports” said Frank Nothaft, Freddie Mac vice president and chief economist.

And that brings us to this graph from Political Calculations based on some of my posts: Predicting Mortgage Rates and Treasury Yields

Using their calculator and a Ten Year Yield of 3.75%, we would expect the 30 year Freddie Mac fixed mortgage rate to be around 5.62%. Current mortgage rates are lower than expected - as they have been since early in 2009 - and some of the difference from the expected rate is probably due to the Fed's MBS purchases (also prepayment speed is a factor - and also just randomness).

The final graph shows the expected mortgage rates (UPDATE: based on formula in previous graph) with Ten Year Treasury yields on the x-axis, and actual mortgage rates from Freddie Mac (weekly) since the beginning of 2009 on the y-axis.

Note: Y-axis doesn't start at zero to better show the change.

There are many factors in determining the spread between the Ten Year Treasury yield and the 30 year mortgage rates (like the supply of new MBS) - but this graph suggests to me that mortgage rates will rise 35 to 50 bps relative to the Ten Year when the Fed stops buying agency MBS at the end of March.