Population density is an important principle for understanding cities. It refers to the number of people per unit of measurement.
So, for example, Provo reportedly has a population density of 2,500 people per square mile. By comparison, New York City has a population density of 27,012.5 people per square mile and Manhattan has a population density of 70,951 people per square mile. Closer to home, Salt Lake City has a population density of 1,666 people per square mile, while Ogden has a population density of 3,113.72 people per square mile. All of these cities, including Provo, have higher densities in some central and downtown areas.
I’ve written repeatedly on this site about the need for high density in a city. This principle is fairly widely accepted today, but Jane Jacobs’ The Death and Life of Great American Cities provides an introduction to the concept.
In chapter 11, “The Need for Concentration,” she argues that a lot of people packed into a relatively small space benefits a city economically and culturally. Citing examples in Boston, New York, San Francisco and elsewhere, she notes that neighborhoods that are able to “unslum” — or, improve their safety, economic vitality, and value — are ones with high densities, not vice versa as is still sometimes still commonly assumed. She writes:
… it still remains that dense concentrations of people are one of the necessary conditions for flourishing city diversity. And it still follows that in districts where people live, this means there must be a dense concentration of their dwellings on the land preempted for dwellings.
Though Jacobs perhaps did not fully anticipate the extreme gentrification that would take place in New York and elsewhere after she wrote her book, the transition of places like Greenwich Village from slums to wealthy enclaves seems to support the idea that density is a financial asset (gentrification, of course, poses its own set of challenges).
One of the most critical distinctions Jacobs goes on to make in chapter 11 is between “density” and “overcrowding.” Early and mid twentieth century urban planning theories often vilified city densities and wanted to thin people out. That thinking produced the suburbs and suburban sprawl.
But Jacobs argues that planners’, and others’, hatred of city densities was misinformed and misplaced. Indeed, she argues that what those people really feared was overcrowding, or the cramming of too many people into insufficient dwellings. Put simply, overcrowding would be putting 10 people in a dwelling suited for five. Jacobs writes
Overcrowding within dwellings or rooms, in our country, is almost always a symptom of poverty or of being discriminated against, and it is one (but only one) of many infuriating and discouraging liabilities of being very poor or of being victimized by residential discrimination, or both.
Jacobs also notes that overcrowding is not necessarily connected to density. Rather, too many people can be crowded into dwellings in low density areas. Though Jacobs doesn’t mention them in her book, some of the slum-suburbs of L.A. illustrate this point. Jacobs actually argues that overcrowding is more commonly seen in low density areas.
Jacobs eventually breaks down how many dwellings per acre she thinks are enough (more than 100, in her opinion). She also recommends adding buildings to low density areas as an improvement strategy, rather than tearing structures down and erecting generic project-like buildings, and notes that frequent streets are essential for making neighborhoods function.
Finally, an underlying assumption in Jacobs’ writing is that a city area needs to support a variety of enterprises and people. She calls this idea “diversity,” which has its own chapter in The Death and Life of Great American Cities.
In essence, she argues that suburbs, for example, have such low concentrations of people that the only businesses and people they can support are those belonging to the dominant culture. A city, on the other hand, includes enough people in a small space that there ends up being a diverse group of patrons and participants in the local economy. That diversity builds on itself, producing more vitality and wealth in cities.