This map was produced in 2011 by Derek Watkins, graphic editor for the New York Times, whose portfolio is full of extremely attractive references (including details on the tools used to produce these gorgeous images). This map was generated by looking on Flickr for geotagged images with urban decay tags. It is noteworthy that the number of images in some cities si quite reduced. In fact, this is not a map of a phenomenon, but of its perception by a group of people whose definition is complex (photographers aware of the special aesthetics of ruins prone to share their images on flickr?). Gorgeous map, anyway, and it seems quite related when it comes to results with other data about this subject.