Morning Report: Why mortgage rates don’t exactly mirror Treasury rates

Vital Statistics:

Stocks are higher this morning on no real news. Bonds and MBS are down small.

First quarter GDP was revised downward from 3.2% to 3.1%. Increased exports offset a downward revision in residential fixed investment (homebuilding). The inflation number was also revised downward and is well below the Fed’s 2% target. The Fed funds futures are now forecasting a more than 80% chance of a rate cut this year.

Initial Jobless Claims ticked up to 215k from 212k the prior week.

In market environments like yesterday, I always seem to get the following question: “Brent, the 10 year is down from 2.4% to 2.25% over the past two weeks. I just ran a scenario and only saw a small improvement in pricing. How come?” The short answer to that question is that mortgage rates are tied to the prices of mortgage backed securities which are influenced, but not determined by the 10 year. (This is why my opening statement always talks about bonds and MBS – they are different animals and will behave differently to changing market conditions)

To make things even more complicated, mortgage backed securities will behave differently depending on the coupon. Take a look below at what a typical MBS screen looks like. This lists the TBAs (stands for to-be-announced) mortgage backed securities that correspond to Fannie Mae loans. If you do a Fannie Mae loan, it is probably going to go into one of these securities. You can see that there is a different security for each month of delivery and note rate. On the far left hand side you can see the coupon groupings. It starts at 3%, then goes to 3.5%, then to 4% and so on. The delivery months are also listed: June, July, and August. Note that the price falls as you go out in the future. This is why a 45 day lock costs more money than a 15 day lock.

During the day, mortgage backed securities will trade and prices will be updated pretty frequently. So, if the 10 year bond rate falls by, say 5 basis points, you could see the implied yield of the Fannie 4% of August drop by 5 basis point, 2 basis points, whatever. It will be a function of the supply and demand for that mortgage backed security. Since these prices are the inputs to the rate sheets you see every day, this is the security that really matters, not the 10 year.

If you take a look at the 4% coupon, you’ll see them trading at just under 103. An investor who buys a mortgage backed security is paying 103 for a bond that will pay 100 at some time in the future. Why would a rational investor do that? The answer lies in the interest. The 4% interest payment is higher than the corresponding rate you would get on the benchmark Treasury, which is 2.375%. That difference is the compensation for paying more than par. The investor is betting that they will get that extra interest for a long enough period to cover the extra 3 points they paid. If the mortgages pay off earlier than expected, then the investor is out of luck. This is why early refinancings are a no-no and why Ginnie Mae is taking action to prevent early refinancings of VA loans.

So, when interest rates fall, like we have seen over the past couple of days, the rates on mortgages don’t fall in lockstep. MBS investors will re-evaluate their prepayment models and figure out the right price to pay given the fact that the period they will get that extra interest has changed. Before, they might have expected to get it for, say 7 years. Now they expect to get it for 6 years. When they crunch the numbers, they come up with a right price to pay for that 4% mortgage backed security. And the price for that mortgage backed security will then be used for everyone’s rate sheets. To make things even more complicated, the change in price for a 3% security will differ from a 4% security. The name for this whole phenomenon is called convexity, and it gets into some gnarly bond math. But the punch line about convexity is that mortgage backed securities have a lot of it, which causes them to behave differently than the 10 year. So, when you see on CNBC that the 10 year bond yield fell 10 basis points, you can’t expect to see a corresponding 10 basis point improvement in mortgage rates. It just doesn’t work that way.

Author: Brent Nyitray

In the physical sciences, knowledge is cumulative. In the financial markets, it is cyclical View all posts by Brent Nyitray