This research provides new data and insight onmetropolitan areas worldwide. It summarizes new data, derived from satellite images of the world at night, to provide systematic estimates of the economic activity generated by cities and metropolitan areas worldwide. It identifies 681 global metropolitan areas each with more than 500,000 people. Taken as a whole, these large global metropolitan regions house 24 percent of the world's population but produce 60 percent of global output, measured as light emissions. Asia leads the way in global economic urbanization according to our findings, followed by North America, the emerging economies, and Europe.