Matt Yglesias puts up this graphic about the relative populations of New York boroughs



Matt forgot why he was making the graph, but to me the interesting thing it shows is how central the New York City subway system is.  Its effects dominate everything else, even the 1970s urban crash.  Arguably, by making urban living in many ways more convenient for urban workers than commuting, it's the reason the 1970s crash was relative mild.  And if Robert Moses hadn't killed off plans for a Staten Island subway line, the population would probably rival that of the other boroughs.