A typical parking space can often be more than 120 square feet—about the size of a standard work cubicle. Bringing a car to work essentially doubles the amount of space that someone needs on the job.

Education is, after January temperature, the most reliable predictor of urban growth, especially among older cities. Per capita productivity rises sharply with metropolitan area size if the city is well educated, but not if it isn’t.

Nine square feet of road space is plenty for a pedestrian walking down Fifth Avenue, and on a busy day, walkers will put up with much less. The Honda Accord, a modest-size car, takes up about a hundred square feet on its own. If that car is going to have a couple of feet around it and several car lengths ahead of it, its space needs can easily

Massachusetts towns have imposed stricter and stricter rules preventing new development and subdivisions. One municipality forbids building anyplace where there’s a “wicked big puddle.”

About half of America’s homes in 2000 were built between 1970 and 2000, so let’s assume that about half of America’s housing stock thirty years from now will also be new. If every prodensity effort is wildly successful in the United States, emissions from driving and powering these new houses might fall by 50 percent.

By redirecting water from farm areas to cities, California could easily provide enough water to sustain much higher density levels, which would reduce America’s carbon footprint.

Over half of American income is earned in twenty-two metropolitan areas.