August 14, 2007

  • How Not To Show Data

    I've been looking at a bunch of Texas history stuff for various reasons, and here's a chart showing how to display information while hiding its importance. It's the black population as percentage, per county in eastern Texas in 1890, as drawn in 1976.

    tex_percentage_black_1890

    If you know the county and want to find out the percentage, you can. But if that's the information you need, then you can just go to the same source the mapmaker went to and get a more accurate number. If you want to see where the black population of Texas in 1890 was concentrated, however, you have to get out your coloring pencils and alter the map, because all the hatching patterns are very similar.

    Compare that map to this one, created the same year as the first, showing black slaves as percentage of population, for the same region only 30 years earlier.

    slaves_population_1860

    It tells you what you wanted to know: Slaves were mostly used in Wharton county, so much so that 80%+ of the population was owned by someone else. And along the rest of the mostly-unpopulated agricultural Gulf coast region.

    So here's my question to you: Why are these maps so different when they display nearly identical information? They seem to have been drawn by the same person. Why is one clear and the other not? Does the latter unfairly point the finger at Wharton county, when neighboring counties also had a high percentage of slaves? Could the blandness of the former be a statement on the evils of slavery, which had been abolished by 1890 and similarly abolished from the map? Is the difference between these two maps a condemnation or a celebration? Or does it seek to hide some kind of racist shame? Or maybe it only shows that the former map's artist could only draw one kind of hatching.

    These are the things I get caught up in thinking about from time to time.

Comments (2)

  • All those maps really say is some parts of Texas are good for growing cotton.

  • I once did a design for a collection of Community Foundations, they wanted charts showing how their endowments had grown, of course there were 50 of them, and some had grown a great deal and others, well... so we "massaged" the graphs. They looked the same but the scales were all wildly different.

    Every map is a political document. Every statistic a politically invented lie.

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