Comment on Sumner's article on Reallocation to housing in 2001

Scott Sumner has an interesting article today about reallocation into housing in 2001.I agree with Professor Sumner's general view that during a slump (or reallocation) the right metaphor is like a bicycle going uphill. Fed is the cyclist pedaling vigorously. But if the effort is not about a certain threshold (NGDP) the bicycle will roll backward. You argue that the effort was below the threshold. I agree with this.
While I understand the simplification, I am not convinced with housing vs...