I talked to Kirk Goldsberry, who teaches cartography at Harvard, about the rise of viral maps. He noted that people tend to be very trusting of maps. Information a reader might be inclined to question if presented as text might be more blithely accepted if presented in the form of a map. This certainly seems to be the case when it comes to the distinctive songs map. If a music critic asserted in a review that Sufjan Stevens is the most listened to act in Illinois, you would be skeptical of that claim. More listened to than Jay Z? Than Katy Perry? Than the Beatles? When incorrectly labeled as “Each State’s Favorite Band,” the map was making such a claim. But in the context of a map, readers were slower to realize the mistake, if they noticed it at all.
Even knowing that the map is showing the most distinct, not the most popular, band for each state, the map can still be misleading if you don’t pay attention to the methodology. For example, Lamere made the decision to only include bands among the 50 most listened to in each state for his sample, so that the map would feature acts with a reasonable level of popularity. Without such a cutoff, the most distinctive band in many states would be a local act many readers would never have heard of. In Virginia, for example, if the cutoff had been the top 1,000 most listened to artists, as opposed to the top 50, the commonwealth’s most distinctive artist would have been HardHittaz—a group that is not in the top 10,000 most listened to groups in the United States.
Lamere’s choice of 50 as a cutoff was therefore reasonable—it produced a map where the majority of the acts are recognizable to most readers—but it was also arbitrary. Below are two maps created using the same methodology and same data that Lamere used, only in these maps, the cutoff is 35 and 100 instead of 50.
As you can see, the choice of cutoff drastically affects the results. Let’s look at Illinois again. When the cutoff is 50, Sufjan Stevens wins out. At 35, the state’s most distinctive artist is the Rolling Stones; at 100, it’s Wilco. Likewise, New York’s most distinctive artist shifts from Bob Dylan to James Blake to Grimes based on whether the cutoff is 35, 50, or 100, respectively. These alternate maps show how fickle data can be.
This is not to say that just because a map goes viral that it is shoddy or misleading cartography. Consider this viral map created by Reddit user Phaenti on the subreddit MapPorn that compares each state to a country with roughly the same GDP. The map was republished widely, including on Slate.
This map may seem purely wacky at first, but it does a great job of illustrating the size of the American economy. You knew Texas’ economy was huge, but you might not have realized it was the same size as a large industrial country like Mexico. Even many small states like Wyoming and Idaho measure up to countries whose population exceeds 50 million. This element of surprise is likely what made the map a viral hit, and rightfully so.
That said, if you really want to know the size of each state’s economy (and their sizes relative to one another), this map isn’t of much use, unless you’re already familiar with the GDPs of nations around the world. (Do you know how Nigeria’s GDP compares with that of the Philippines? Probably not.) But you also probably wouldn’t bother sharing this map on Facebook:
Given the inherent limits of most viral maps, you might expect professional cartographers to dislike them. But people who love maps love maps. Harvard’s Goldsberry sees viral maps as merely the latest chapter in a long, fruitful history of amateur mapmaking. I also asked Ian Muehlenhaus, a professor of cartography at University of Wisconsin–La Crosse, what he thought of these simple state maps. “Are these maps useful tools for learning? Most of the time, no,” he said. “Does that mean these maps are bad? No. They are damn entertaining!”
I’d been wary of making my own state maps, but the enthusiasm of these cartographers made me think that maybe they aren’t so problematic after all, especially if the mapmaker is as clear as possible about his methodology. So I built some maps of my own. Do they fall into the same pitfalls that other simple U.S. maps do? Probably. Do New Yorkers never name their daughters Brooklyn, or do they just love Brianna more? Do people from Massachusetts dislike Gladiator or are they just really obsessed with The Departed? Is it fair to say Colorado’s “most distinct” vice is marijuana, when more people in the state still smoke tobacco? These maps don’t answer these questions. But hopefully they’ll entertain you! Just don’t forget to read the fine print.
Correction, May 1, 2014: The countries of Jamaica and Djibouti were originally misspelled in the maps interactive.
See more of Slate’s maps.