Demographics, Maps and Problems

One of the things I love about maps is how they can tell you a lot, just by looking at them. Of course, maps based on statistics are just like the statistics themselves -- depending on how you use and frame the data, you can sometimes make them say what you want them to say.

Take for example Detroit. We drove to Detroit last year to see if it really was as bad as what people say. People love to talk, and say things, and sometimes exaggerate because it makes for a better story. We wanted to have the opportunity to see with our own eyes if it really was a failed city.

No map could describe how awful the city was. We drove not only around downtown, home of empty skyscrapers, some of which have been turned into parking garages because no other use could be made of them, but we also drove through the residential areas north of downtown. Abandoned houses abound, most overgrown with weeds and boarded up. On each block, every single block, there was at least one burned out house. Burned by its desperate owner in order to collect an insurance payment and move on?

But I wonder how many houses are actually vacant in Detroit?


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The scale maxes out at 60%, and note that there is actually a part of downtown Detroit that reaches that. It's probably something to do with the airport being in that block. Sometimes the statistics themselves are inconsistent in what they define as a "housing unit", but nonetheless most of downtown is around the 30% vacancy mark. Imagine one out of every three houses on your street being empty.

Los Angeles by comparison is doing pretty well. The parts with high vacancy rates along the coast to the northwest of downtown LA are Malibu. Holiday homes?

Another demographic collected by the U.S. Census Bureau, which I find a bit surprising, is race. "Race" in the simplest, schematised way you could imagine it. Someone who is the 12th generation descendant of slaves brought to the United States before it was the United States, and someone who is on a student exchange from Botswana might both be counted as exactly the same thing by the census, if they were both "black".

But as someone pointed out to me, after discussing the fact that they'd written "Race: White" on a fix-it ticket my husband received while driving in Maryland with one headlight out, only if you track things like "race" can you point out that people with dark skin get more tickets.

Washington, DC is a lovely city. I was blown away the first time I visited, because I had very low expectations. Never have I seen another American city with such grace and vibrance. Manhattan is amazing, but gruff. Boston is decidedly English, in many senses. Los Angeles wears microshorts, and San Francisco wears hemp. DC wears tailored suits and an authentic, but understated Rolex.

But there's something fishy about the parts of DC I've spent most of my time in during my few visits. I thought DC was "black". Where are the African Americans in Dupont Circle and Georgetown?


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Notes: The scale goes from 0 to 100%, and represents the proportion of "black" inhabitants in each census block in DC. The white-coloured areas of the map actually mean "not black", and other "races" are not factored in at all.

There are virtually no inhabitants who self identify as African American in the government and fancy neighbourhoods of DC.

But I don't like cutting off a map at an administrative border, and excluding immediately adjacent areas. I wonder what it's like in neighbouring counties in the states of Virginia and Maryland...


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Oh, dear.

Data used
U.S. Census Bureau Tiger/LINE shapefiles downloaded from the ESRI website. I used Census Blocks and Census Block Demographics (SF1) for the 2000 census.