because that is a big one - its not like Americans are having more and more kids - In the US, I think we are a little more than replacement level and trending downward.
Throw in: 1. inflation via increased money supply through multiple rounds of stimulus but other federal government spending. 2. Historically low, sustained interest rates - money is cheap and sellers can sell for more, 3. More dual income families drives up peoples ability to pay and what sellers can sell