[Shivetya]

Yet in nations that have recently moved into the income levels needed for automobiles their usage has exploded. China, India, and a few others, all seem to be burgeoning car markets.

I think one area over looked in their study of people streaming into and out of cities is the less need for the city itself to provide for the needs of the people. Combine that with all the congestion style pricing and it drives development outside of the city where those who cannot afford the entry costs.