Nathan Yau's data visualization maps the food deserts in the United States. Image: Nathan Yau The length of the red line corresponds to the distance a town is from a grocery store. The longer the line, the farther people have to travel. Image: Nathan Yau Sparsely-populated states like Wyoming mean lots of long red lines. Image: Nathan Yau Texas is an excellent example of visualizing population density in reverse. Image: Nathan Yau If you reduce the radius, you'll start to see how food deserts affect more urban areas like Chicago. Image: Nathan Yau Montana is more populated in the west, as visualized here. Image: Nathan Yau

Next time you’re going to complain about lugging a few bags back from the grocery store on foot, you should really take a look at Nathan Yau’s most recent data visualization. The statistician behind Flowing Data has plotted the nation’s food deserts, which by definition is any place residents have limited access to grocery stores, and it’s pretty staggering how far some people have to travel just to pick up common goods.

A couple months back Yau looked at the location of major grocery stores across the country—which parts of the nation shopped at HyVee, which shopped at Publix and so on. If you mentally overlap the maps, you start to see gaping holes where there’s seemingly no place to buy food at all. “That eventually got me wondering about the reverse,” Yau says. “Where there aren't many nearby grocery stores.”

Using the Google Places API, Yau search for the nearest grocery store every 20 miles (this included smaller stores–not just the major chains he plotted in his last visualization). “I chose those increments, because there's some rough agreement that a food desert is a place where there isn't a grocery store within 10 miles,” he explains, adding that in pedestrian cities the standard is closer to a mile. “And if you consider searches every 20 with a 10-mile radius you've got a fairly comprehensive view.”

Zoomed in, each dot you see on the map is a grocery store, and the red lines represent how far a town is from the nearest. The longer the line, the farther the distance from a store. If you’ve ever driven across Nevada on the Loneliest Highway, it makes sense that the state is covered in red starbursts until you get to the areas surrounding Las Vegas and Reno. Likewise, if you zoom in on Montana, you can see how the length of red line increases gradually as you move into the eastern, more mountainous part of the state. And the spots where the red lines are faint or fade into the background? Those are the spots where groceries are aplenty.

The map is an interesting look at reverse population density, and it does take stock of a very real problem. But it would be fascinating to be able to zoom in and analyze the issue more closely at the urban level, where food deserts are a major concern. Yau touches on this idea in the original post, and concedes, "Of course, there are still other considerations like transportation, food cost, and population, but I think this view is a good start."