In fact, there are two types of density, according to a recent study by Peter Gordon of the University of Southern California and Sanford Ikeda of the State University of New York, Purchase.

WSJ: To Build Creative Cities, the Sky Has Its Limit by Richard Florida

As I describe above, the 2000 favelas in the municipality of Sao Paulo are a vast terrain whose expanse and extreme population density are a deterrent to easy policing and even state military action.

FORBES: Curfew In The Favela