Most of the world’s research and entrepreneurship is concentrated in a few megacities.Innovation is geographically uneven. The world’s 40 richest mega-regions — expansive conurbations such as the Boston–New York–Washington DC corridor, Greater London, or the passage that runs from Shanghai to Beijing — account for more than 85% of the world’s patents, and 83% of the most-cited scientists. And yet, only 18% of the world’s population lives in them.