Reader Stephan sent an email asking, “The fed dropped rates, so why aren’t mortgage rates dropping?”
Great question! I know a lot of people hear the news — Fed Lowers Rates 0.75%! — and they expect that mortgage rates do the same.
Not so much.
The “emergency rate cut” the Fed took on Tuesday dropped the “Fed Funds” or overnight bank to bank lending rate 75 basis points (0.75%). So why didn’t mortgage rates also fall 0.75%?
Because the fed funds rate and mortgage rates aren’t “correlated”. They aren’t tied together so that when one falls the other falls (or when one rises, so does the other). Sometimes they do, sometimes not.
Let’s look at a graphical representation of the correlation between the Fed Funds rate and mortgage rates.
This chart is a “scatter plot”. Each point represents a fed funds rate and the corresponding mortgage rate. The data is from 1971 through this week. The fed fund rate is on the X (horizontal) axis, and the 30 year fixed mortgage rate is on the Y (vertical) axis:
So how do you interpret this thing?
Notice the red box. All those data points jammed in there are telling you that when the fed funds rate was between 1% and 4%, the 30 year mortgage rate was between 5.6% and 6.1%. So a 3% spread in fed rate resulted in a spread in mortgage rates of only 0.5%.
Notice the green box. All those data points are saying, “Look! When the fed funds rate is 6.3 to 6.8%, the mortgage rate can be anywhere between 7% and 11%.” A 0.5% spread in fed rate can corresponds to a 4% spread in mortgage rates.
In other words, the correlation between fed funds rate and mortgage rate is not good. Just because one rate rises or falls it doesn’t really mean the other will.
(Before some statistics wizard jumps all over me, yes the chart indicates some positive correlation. In fact, the correlation coefficient is 0.79. But as a good stats wiz knows, correlation coefficient as a summary statistic shouldn’t replace examination of the data. Just look at Anscombe’s Quartet.)
How the fed funds rate, mortgage rate and every other interest rate out there are manipulated, and the factors that cause them to change is very complex. I am not an economist (nor a lender), just an interested bystander.
In a nutshell, the Federal Reserve controls short term rates (such as the rate that was cut on Tuesday). Mortgage interest rates are not controlled by the Fed, they move up and down based on the trade in mortgage backed securities / the mortgage bond market.
I vaguely remember Dr. Duck (his real name), my undergraduate economics professor, saying something along the lines of the Fed primarily manipulates the Fed Funds rate to control inflationary pressure, provide liquidity to the financial markets and to try to balance employment rates, prices and economic growth.
Want to learn more?
Texas A&M Real Estate Center: The Fed Rate vs. Mortgage Rates
Here is a nice summary article on interest rates: Interest Rates 101.
And from one of my favorite web sites, How Stuff Works, come these series of articles that may be of interest: How the Fed Works, and How Interest Rates Work.
The Federal Reserve itself chimes in with, “In Plain English: Making Sense of the Federal Reserve”. (PDF)
[tags]Fed Funds Rate, mortgage rates, financial policy[/tags]
I'm Jay Thompson, and I have a little blogging problem... 
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