Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Why do 10 year Treasury bond yields affect mortgage interest rates?
The yield on treasury bond indicates the amount of money anyone at can make at virtually zero risk.   So lets say banks have X [say 100] amount of money. They can either invest this in treasury bonds and get Y% [say 1%] interest that is very safe, or invest into mortgage loans [i.e. lend it to people] at Y+Z% [say at 3%]. The extra Z% is to cover the servicing cost and the associated risk. (Put another way, if you wanted only Y%, why not invest into treasury bonds, rather than take the risk and hassle of getting the same Y% by lending to individuals?) In short, treasury bond rates drive the rate at which banks can invest surplus money in the market or borrow from the market. This indirectly translates into the savings & lending rates to the banks' customers.