Patterns of gentrification vary by city, and the spread of gentrified areas is partly determined by the city's predominant development form and the historic levels of African-American populations within them.

Gentrification is a nuanced phenomenon along these characteristics, but most people engaged in any gentrification fail to acknowledge the nuances.



Spurred on by the recent debate on the impact of limited housing supply on home prices and rents, thereby "capping" gentrification, (taken on fantastically by geographer Jim Russell in posts like this), I decided to do a quick analysis of large cities and see how things added up. The analysis was premised on a couple of observations of gentrification, one often spoken and one not.

One, gentrification seems to be occurring most and most quickly in cities that have an older development form, offering the walkable orientation that is growing in favor. Two, gentrification seems to be occurring most and most quickly in areas that have lower levels of historic black populations. This less noted observation was the thrust of a study by Harvard sociology professor Robert Sampson and doctoral student Jackelyn Hwang, recently described here. Here's what they said, after conducting an exhaustive study of gentrification patterns in Chicago:

After controlling for a host of other factors, they found that neighborhoods an earlier study had identified as showing early signs of gentrification continued the process only if they were at least 35% white. In neighborhoods that were 40% or more black, the process slowed or stopped altogether.

That prompted my quick study. I wanted to categorize cities by old and new development forms, and low and high historic levels of black population. To do that I came up with an arbitrary proxy for the age of development form. Using decennial Census data, if a city reached 50 percent of its peak population by 1940, it was deemed to have an old development form; if a city reached 50 percent of its peak population in 1950 or later, it was deemed to have a new development form.

Here's a quick example of how this works. Baltimore, currently with a population of a little over 600,000, reached its peak of 949,000 in 1950. Baltimore reached half its peak, or about 475,000, by 1890, a time at which it could be said that Baltimore's form as a city had been firmly established. Similarly, Austin reached its peak of 790,000 in 2010. The fast-growing Texas city was half that size in only 1990, a year in which it could be said that its development form was established and the city began to see itself as a major city. Imprecise, yes, but a decent proxy for examining old and new city development forms.

The second piece of analysis was gathering Census data on central city black populations in 1970. This decade was chosen largely because it represents the end of the Great Migration, when millions of African-Americans left the rural South for cities across the nation. By that time the cities that are generally recognized as having large black populations had already been identified, and it is possible to explore the impact of the migration on them. I arbitrarily said cities with black populations lower than 25 percent of the total in 1970 had a low black population, and those above 25 percent had a high black population.



Using those two factors, I put together this table of the 64 primary cities over 250,000 in the U.S.:

Pete Saunders

More than a few cities are exceptions, largely because recent consolidations or large-scale annexations have boosted them into more unfamiliar boxes. But some patterns are evident, and if you think of these in terms of gentrification, you might be able to make the following general assumptions:



Old Form + Low Black Population = Expansive Gentrification (OFLB)

Old Form + High Black Population = Concentrated Gentrification (OFHB)

New Form + Low Black Population = Limited Gentrification (NFLB)

New Form + High Black Population = Nascent Gentrification (NFHB)



Identifying the examples might be the best way to explain what I mean. New York, San Francisco, and Boston are the prototypical OFLB cities, and gentrification has made its widest impact in these three cities. Chicago, Washington, and Atlanta are the classic OFHB cities, where gentrification is concentrated in certain areas of the city (or region), and eludes the heavily African-American parts of the city.

Phoenix, San Diego, and Las Vegas might be the prototypical NFLB cities, all of which came of age with the car as the dominant mode of transport and with few African-Americans. NFLB cities may also be the leaders and innovators in seeking ways to catalyze their inner cities, with greater tangible investments in public transit and mixed-use development. The relatively few NFHB cities are a distinctly Southern phenomenon, and by all appearances gentrification activity lags behind other cities, with sprawl still the dominant development engine.



Why would any of this matter? Nationally, the gentrification debate is defined by the experiences of the OFLB types like New York, San Francisco, and Boston. There, the issues are rapidly growing unaffordability, concerns with displacement and growing inequality. But the gentrification debate is quite different in OFHB cities like Philadelphia and Atlanta, where seeking ways to more equitably spread the positive benefits of revitalization might lead such discussions.



In other words, it's not exactly correct to look at what's happening in Los Angeles or San Diego, or Baltimore or St. Louis, in the New York-San Francisco-Boston context. Different forces and different experiences are creating different outcomes in each city, and if we want to understand how to look at gentrification's impact, we need to understand its foundations.