Sprawl accounts for only a small slice of America’s civic decline.

Evidence

The fraction of the population living in metropolitan areas has grown by roughly ten percentage points since the mid-1970s, and the civic penalty associated with such areas is, in round numbers, 20 percent, as suggested by figure 50, figure 51, and our analysis of the effects of commuting time. If Americans still lived spatially where we did in the mid-1970s, the aggregate level of community involvement might be roughly 2 percent higher, as compared with the drops of 20–40 percent registered in section II. This calculation is rough-and-ready and disregards synergistic effects. — Robert D. Putnam, Bowling Alone The Collapse and Revival…, 2179