For his “Growth Rings” project, the data visualization artist used U.S. Census data to map where America’s population had moved to between 2000 and 2010. When the results came in there were obvious answers: “New track developments appear to be sucking the life out of the older neighborhoods,” he wrote in a blog post accompanying his maps. Then he noticed a tiny spot of hope in, of all places, Detroit. Among all the red showing the neighborhoods people had left was a patch of blue showing population growth right smack in the middle of downtown, even though the city had lost a quarter of its population in that span of time.