Wednesday, January 14, 2015

A City Can Be Diverse, but its Neighborhoods Might Not Be. DC Scores Poorly on Both Measures

The diversity of each census tract in DC.

How do you measure a city's diversity? If a city has a lot of different racial and ethnic groups in their own segregated sections, is that diverse? A blog called priceonomics recently ranked major American cities on diversity by looking at the percentage of major racial and ethnic groups within the city's limits. The District of Columbia came in 21st, slightly less diverse than Oklahoma City. 

However, while this analysis is useful, it it doesn't reveal whether the neighborhoods in each city are themselves diverse, or whether the city boundary just encompasses some all-black areas, other all-white areas, and so on.

If we modify this methodology to measure the average diversity of a city's neighborhoods, rather than of the city as a whole, we are able to quantify how integrated these place are. On this new measure, the District performs even worse.

A Neighborhood-Level Calculation Changes the Results

Consider Chicago. With roughly equal-sized black, white, and Latino populations, the Windy City ranks as the fifth most diverse city in the country on the priceonomics scale. However, if we instead use priceonomics' same methodology (it took the percentage of black, white, Asian, Latino, and other people in the city, then used a Herfindahl-Hirschman Index to combine those numbers into a single score) for each of Chicago's individual census tracts, then take the weighted average, Chicago suddenly drops to 38th out of 45.

(Click a city's name to view its map)
NameNew RankDiversity Index
(Neighborhood)
Original RankDiversity Index
(Citywide)
Rank Change
Sacramento10.32477820.2493451
Oakland20.36768210.234220-1
Long Beach30.40482440.2853671
Fresno40.419840150.33261611
San Jose50.41991260.2959631
San Francisco60.42005080.3118102
Las Vegas70.439887170.33810610
San Diego80.46835190.3127091
Fort Worth90.478435130.3246714
Albuquerque100.482462270.39906417
Charlotte110.495846160.3369055
Boston120.49635170.310615-5
Austin130.500739190.3712116
Oklahoma City140.502493200.3743756
Virginia Beach150.510308330.45543618
Raleigh160.512390220.3810926
Houston170.518201100.313724-7
Tucson180.518248260.3990558
New York190.52082730.260531-16
Jacksonville200.524788250.3985755
Los Angeles210.526386180.339228-3
Dallas220.531520120.321215-10
Denver230.536938240.3874161
Nashville240.538537290.4088575
Seattle250.545698370.47687612
Mesa260.553278380.49269412
Phoenix270.556085230.384986-4
Indianapolis280.565431310.4226303
Columbus290.565687320.4305333
Colorado Springs300.565902410.52823311
Portland310.569062430.53941712
San Antonio320.574919350.4746363
Kansas City330.579408280.399368-5
Milwaukee340.589951110.320661-23
Philadelphia350.599411140.331147-21
Washington360.611801210.378045-15
Omaha370.613333390.5010412
Chicago380.63299350.290745-33
Louisville390.656964400.5181451
Memphis400.670075340.474338-6
Atlanta410.670933300.416675-11
Baltimore420.681552360.475331-6
El Paso430.706141440.6633451
Miami440.732796420.536259-2
Detroit450.795764450.6741850
Note: Priceonomics used the 2013 1-year American Community Survey estimates for their analysis. This analysis uses the 5-year estimates, because it is available at both the Place and Census Tract levels. As a result, the citywide index scores may vary slightly from the data presented by Priceonomics.


Chicago, as a whole, is diverse, but its neighborhoods are not. The average Chicago census tract is less diverse than a typical tract in Portland or Colorado Springs, both relatively homogeneous cities that scored near the bottom in the original citywide index. Both are close to 70% white, but the non-white population isn't all clumped in a small non-white area.


Chicago's diverse population is largely segregated. Sacramento is diverse, and so are its neighborhoods.


California cities dominate the adjusted rankings, accounting for the top six spots: Sacramento, Oakland, Long Beach, Fresno, San Jose, and San Francisco. Virginia Beach moved up 18 slots, representing the largest jump of any one city.

DC, on the other hand, drops into the bottom quartile, neck and neck with Omaha. Like Chicago (well, not quite as bad as Chicago), the District's citywide diversity doesn't extend to diversity within most of its neighborhoods.

How Citywide Diversity Relates to Neighborhood Diversity

There is a correlation between diversity in a city and diversity within its neighborhoods, although places like Chicago and DC remind us that it is not necessarily as strong relationship. Here's a scatter plot comparing the citywide and neighborhood average diversity indices for each of the 45 cities:

Diversity within neighborhoods compared to overall city diversity, with the most integrated and most segregated cities labeled.

Cities above the trend line have less diverse census tracts than the city's overall diversity would suggest. These are therefore relatively segregated. Chicago and DC fall into this category.

Miami is among the least diverse cities on the entire list (remember that according to this methodology, "diversity" only considers 5 distinct groups, lumping together, for example, everyone who identifies as Hispanic/Latino), but on a neighborhood level it's even more segregated still.

Cities below the trend line have neighborhoods that are more diverse than comparable cities at their level of citywide diversity. This group includes Sacramento, which is both diverse and integrated, as well as Portland, which is not diverse, but relatively well-integrated.

Diversity and integration are both important, and the District has a long way to go on both measures.

Cross-posted at Greater Greater Washington

Thursday, June 26, 2014

Visualizing Sprawl

Some big US cities are dense, while others are spread out. This affects the economy, quality of life, and the environment. Here's a way to visualize the residential density of the country's 12 largest regions and their varying levels of sprawl.

Residential density of census tracts in and around the District of Columbia and Baltimore
(magnified 200% in each direction, relative to visualizations below)

Earlier this year, Smart Growth America released a report titled Measuring Sprawl 2014, finding that New York is the country's "most compact, connected large metro area," with an index score of 203.4, while Atlanta is the "most sprawling," with a score of 41.0.

But what does that gap really look like? The world's most iconic skyline on one extreme, contrasted with a highway full of motorists stranded overnight due to a snowstorm on the other? What about viewed through a wider angle lens, at a regional level? Next City recently published a series of GIFs illustrating regional sprawl over time, and this post tells a similar story from a different perspective.

The visualizations below show residential density (as one unit of height for every person per square mile), by census tract, for the nation's 12 statistical areas of at least 5 million inhabitants. The images show Combined Statistical Areas (CSAs) with the exception of Miami, which until recently was not part of a CSA. The regions are viewed from the same height and distance, but from different directions, most often from the south.



Note: One census tract, 307.2 in Chicago, was omitted from this visualization as its population density is off the charts. The tract essentially encompasses only the land on which these three high rises are located.

Cross-posted on Greater Greater Washington

Friday, April 4, 2014

Where Are DC's Corner Stores?

Originally Printed/Posted in the Washington City Paper on February 26, 2014

Displaying Corner Store GraphicV3.jpg

Sure, you know the place down the block from you, and maybe the one a couple of streets over. And the one by your friend’s house where you sometimes stop by to pick up a six-pack on your way to visit. But how many corner stores are there in the District, all told?

Defining them is more art than science, but here’s a stab at systematically identifying all of D.C.’s businesses that fit the bill. Each of these establishments has an active retail license to sell alcohol, cigarettes, groceries, and/or food products, in a building and property of less than 10,000 square feet, located within 150 feet of a zone that allows residential development. Chain grocery stores and pharmacies don’t count, nor do gas stations.

That adds up to more than 500 stores. Quite a few of their names give deference to “The Corner” (Charlie’s Corner, Cookie’s Corner, Cornercopia) or to the intersecting streets that form the corner (18th & D Liquors) or both (11-M Corner Market). Many are joint ventures: P&C, B&M, K&H (and just about every other possible permutation), Stop & Go, Me & My, Night N Day.

This map shows where these corner stores are located and identifies some of the neighborhoods blessed with the highest concentrations of such establishments. The densest stretch? A strip near Kennedy Street and Georgia Avenue NW, with one store for every 170 residents of the surrounding blocks.