That sort of metric is nigh useless at a national level. Real Estate / Housing is one of the most regional things, such that two adjacent square miles can have wildly different results.
If I had to guess, for the past couple of years we've been in a period where even more than usual, activity is segregated to a certain minority of regions or sub-regions. Makes national numbers look one way and then you look around your local area and wonder "wtf?"