When I asked urban planners and urban engineers why they built so many buildings per region, most of them pointed to economic reasons.
That is, they argued that if more people lived in cities, they could afford to build more.
Urban planners, however, argued that such cities would have more people in them, and that people would move to cities where they could work, live, and work, which would create more jobs.
Urban engineers, however — and urban planners in general — argued that more people and more jobs would increase the number of jobs and jobs would decrease the number in each city.
They didn’t offer a way to determine whether cities would become more or less dense by building more.
But if urban planners’ arguments are true, they would make sense if the demand for housing in each region were high enough to increase the demand per building per city.
In practice, though, they tend to be wrong.
For example, if the region of New York City were to double its population from about 8.5 million to about 12 million, that would increase housing demand and require more buildings per area than if New York had stayed flat.
As a result, if you look at population density in each state, you can see that cities tend to get denser and denser denser.
In some states, the number is so high that the population density per city can be measured.
In other states, it’s lower, but still very high.
And in most states, a single-family house is the most common type of house in a city.
This chart shows the density of housing in the 50 largest U.S. metropolitan areas.