> Interest rates are a much more likely culprit.

To expand on that a bit: Supply and demand in houses doesn't work on the price. Supply works on the price; demand works on the monthly payments. When interest rates go down, the same people can now spend more on a house for the same monthly payments, and so the price rises.

It would also be worth looking at the geographic distribution. I suspect that most of that growth is from urban areas. Which, then, would also reflect the ongoing urbanization (and corresponding rise in demand).