m on April 17th, 2013

Pete sent out this New Yorker interactive web thingy that handsomely redraws each MTA line as, instead, a graph of median income rising and falling as the trains move between poorer and richer neighborhoods. I figured it would take only a few hours to throw something similar for Chicago, and I was right.

Below are each CTA line’s stations plotted against the median income of the census tract that contains the station.1

So we can see that there are similarities with the MTA. As trains move into the Loop (Manhattan), the median income rises, and then it falls as trains move back out of the Loop (Manhattan). As with the New York data, we can see some pretty distinct variance in median incomes. The Green Line moves from nice (but not as nice as nearby) Oak Park to some of the poorest parts of Chicago before emerging in the Loop, only to bend south through some more of the poorest parts of Chicago. The Purple Line starts at the super tony Linden stop in Wilmette before moving through less fancy Evanston on its way to the Loop.

What’s going on at Sedgwick? Census tracts are marked in purple. (click to enlarge)

In short, the graphs affirm most of what we already knew. Though I also was not expecting the Blue Line to be so much nicer between Western and Grand than it is in the Loop.

There’s also at least one startling hiccup: the huge dive in median income at the Sedgwick stop on the Brown and Purple Lines. I double checked everything, and that’s the correct tract number. I can only guess that there’s a residual effect of Cabrini-Green’s ghost that’s pulling that number down. Even so, however, the Sedgwick census tract is bordered by North, Sedgwick, Division, and Larrabee, meaning that it’s one tract to the east of Cabrini-Green (which was west of Larrabee) and one tract to the north of the Frances Cabrini Homes, which are south of Division. [UPDATE: I tackle the Sedgwick question in a separate post]

But part of putting this data together was to test another, unrelated hypothesis. I’ve long suspected that the CTA ignores poorer neighborhoods of Chicago, considering how the lines don’t even make it out to the southwest side, and it feels like it’s merely the lowly Green Line fighting its way valiantly to serve the mass of lower-income areas of the West Side. These graphs speak to neither. Also, they don’t tell us whether truly rich areas are served by the CTA, since we have no idea how high that median income number can go. As a result, as is often the case, it’s now more useful to make a map (interactive version available on GeoCommons):

Screen Shot 2013-04-17 at 13.29.50

What I was not expecting to see was that the primary poorer part of the city abandoned by the CTA isn’t the area around Marquette Park on the southwest side (which uniformly sits comfortably in the second of seven bins), but, rather, the southeast side, made up of the South Shore, East Side, and South Chicago community areas. I always assumed this area to be more prosperous, but the median income tale suggests otherwise. The wealth of the southeast side is still along Stony Island and Jeffrey, in from the lake.

Furthermore, it’s not the Green Line coursing through the lower-income West Side by itself; it’s joined by both Blue and Pink Lines.

But this then prompts yet another question. Does money follow the CTA or is it the other way around?2 The median income is higher in tracts near the Red and Brown Lines on the North Side than it is for latitudinally parallel patches of land closer to the lake, where one might expect to find more money. I also doubt anyone would be surprised if it turned out that a large part of Bucktown, Wicker Park, and Ukrainian Village’s appeal to higher-income types are their sitting right on the Blue Line, making travel into the Loop for work trivial.

But the CTA doesn’t guarantee a (relative) level of prosperity. The two final stops on the Ashland side of the Green Line look like they’re doing the opposite, as they’re surrounded by low-income neighborhoods, with the better off tracts farther, rather than closer to the El. Englewood has a low median income but sits right on the Green Line. Beverly and Ashburn, on the other hand, are better off but serviced only by Metra. I recall back in the mid-90s, when the Green Line was being renovated, that people wanted it torn down along 63rd St. precisely because it was a blight. No one wanted to live by the El, and no one wanted to have shops underneath it. I strongly doubt that opinion is uniform throughout the city.

Anyway, in closing, one truly sad thing about living in Vilnius is that I couldn’t toss together this kind of a bit of data visualization about it without leaving my chair and in only a few hours.

  1. In greater detail: I used the 2011 5-yr ACS data on Cook County as provided by FactFinder and joined that with a shapefile of all of the census tracts in Cook County provided by TIGER. Then I pulled in the CTA shapefiles from the City of Chicago (I had actually already done this, but whatever). There were a couple spatial joins and blah blah, and I ended up with a census tract for each station. Many stations straddle census tracts, but I let the spatial join be the arbiter. Then I filtered down the median income dataset to include just the tracts with stations, exercised some patience while dealing with Tableau, and there you go. []
  2. Obviously I could piece together some sort of answer using historical data, but for now I’ll leave it to speculation. []

Tags: , , , , , , , ,