The complexity is this:

> Suppose you buy a home for $500,000, financing the purchase with a mortgage at a 6.4 percent interest rate. A few years later, you sell for $600,000. Interest rates have fallen, and the new buyer is able to get a mortgage at 4.7 percent.

> The price of the home has risen by 20 percent, so you could just say the cost of housing has gone up 20 percent. But that would be misleading. Assuming a 20 percent down payment, your original mortgage would have cost $2,502 per month, while the new owner’s mortgage would cost $2,489 per month. The monthly mortgage payment required to own the home actually went down.