> the mortgage interest rate is almost always fixed It's policy. The New Deal created a secondary mortgage market through Fannie Mae (and later Freddy Mac) th

> the mortgage interest rate is almost always fixed It's policy. The New Deal created a secondary mortgage market through Fannie Mae (and later Freddy Mac) that normalized mortgages to 30 year fixed. There are many ways to structure mortgages in the US and not all mortgages are fixed, but the typical mortgage is because those mortgages are the most liquid given the structure of the US secondary mortgage market.