“Towns are misunderstood orphans that were lost in translation,” says Dijkstra. While “town” versus “city” is a clearly understood distinction in English, he says that Dutch, French, German, and Spanish all lack an equivalent term.

But in defining this third category, Dijkstra argues, we have a more accurate understanding of what the world really looks like1 — a gradient between rural farmers and city dwellers. Those towns, moreover, are the cities of the future.

This more accurate picture matters because simple stats like a majority-urban planet justify the allocation of enormous sums of foreign aid and domestic spending. For example, the 2015 announcement of the German government’s €100 million fund for climate-friendly urban infrastructure leads with that claim. In Egypt, places listed as rural agricultural settlements on official maps are actually cities as large as 275,000, but making the official change puts the government on the hook for everything from schools to courthouses.

Among the other findings that caught this small army of PhDs in urbanization by surprise? “We had no idea that roughly 20 percent of cities in the world are shrinking,” says the OECD’s head of urban statistics, Rudiger Ahrend. “It’s getting more common in countries where the population has started to stagnate or decline.”

These tidbits are just a few of the potential outcomes for this new global definition of cities. Countries already submit statistics about their cities annually as part of their progress reports toward the UN’s Sustainable Development Goals. These goals include indicators like air quality and access to public transport that, until now, were susceptible to fudging the numbers.

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• 1. According to the new definition, which defines a city as a contiguous geographic area with at least 50,000 inhabitants at an average population density of 1,500 people per square kilometer, about 48 percent of humanity lived in cities as of 2015. (This definition roughly corresponds to the “metropolitan statistical area” used in the U.S. Census.) Why the sudden decrease? Because over a quarter of the planet lives in towns — like those Danish hamlets of 200-odd souls — a category that the world has largely ignored in its preference for an urban-rural binary, the idea that someone either lives in a city or in the countryside.