If you want to understand the global economy, look at an aerial photo of the world at night. It is, quite literally, enlightening: Unlike typical maps, delineated by so many politically drawn boundaries and pastel tones, the world after dark sheds light on what unites us, beyond the city or suburb or state in which we live.

At night, the mega-regions of our global economy — areas like greater New York, Boston and Philadelphia in the U.S., or London, Paris and Lyon in Europe — are aglow, thanks to their interconnected cities and suburbs, highways and train lines, businesses and industries.