“I thought the markets determined interest rates”
Not necessarily. The Federal Reserve Discount Rate has a LOT to do with it.
Here are a couple of articles: How the Fed Affects Interest Rates
http://www.life123.com/career-money/real-estate/mortgages/how-the-fed-affects-interest-rates.shtml
http://beginnersinvest.about.com/od/banking/a/aa062405.htm
Yes, I did know the Fed Discount Rate does affect interest rates.
But the discount rate is largely symbolic. It is the rate for very short term transfer of money. 1-3 weeks, anything longer and the bank will get a call wanting to know what they are doing.
But this does have a steering affect on bank lending.