The churn survival option for cities involves their outward expansion

The Economist (Sep. 18, 2010) has this interesting piece re Chinese cities which includes this sub-head: "Policymakers should embrace mega-cities. Businessmen should escape them." What does that mean?

The piece alludes to city rankings that generally display "stability at the top" of the rankings but "churn further down." Wendell Cox has assembled U.S. decennial population data going back to 1950 at Demographia. These are for urbanized areas and their core cities. Just considering the 1950 top ten and over the six census years, the urbanized areas show 22 changes in rankings (of 50 possible), but the core cities show 27 changes. But for the 1950 top five, the urbanized areas show just three rank changes while the core cities show seven; for the next five it is 19 vs. 20.

More stability at the top and more stability for the larger spatial units. Metro areas survive by churning industries and by decentralizing. The suburbanization safety valve is vital and facilitates the churn.

It is well known that Number One did not budge. The New York urbanized area has long stayed on top and the New York core city has stayed on top. Both places have strong and durable advantages. As the world changes and new technologies displace old, the area is able to "churn" industries.

Yesterday's WSJ has a piece on Detroit "Motown Becomes Movietown ...Hollywood has a new favorite location. The Motor City is luring films and TV shows ..." Industrial churn may even bring back Detroit.