Not that you probably needed this, but Fortune has made a map, via data from Square, that illustrates the "Playa Effect" on various S.F. neighborhood during the week of Burning Man this year. Newsflash: Businesses in the Mission saw a big slump in sales.

We've all observed — and relished in — the city emptying out during that last week in August, year in and year out, ever since Burning Man became a thing. But is it the whole city emptying out? Obviously not. It's the neighborhoods that are filled with rental properties and contain large populations of twenty- and thirty-somethings.

The data source could be skewed just based on the penetration of Square software itself in the retail sphere, but it shows a 20.6 percent drop in sales in SoMa for the week of August 25 to September 1. (The map, misleadingly labeled, compares sales for Burning Man week to those of the previous week, 8/17 to 8/24.)

Overall sales in the Mission were down 11.1%, and in Noe Valley and the Castro they were down 11.6%. Burners also appear to be prevalent in Potrero, Hayes Valley, NoPa, and the Haight.

It would be more accurate, probably, if Square data could be combined with survey data from merchants who don't use Square, of whom there are still thousands. But anyway, it's always nice to see a visual.

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