"What qualifies as a "global city"? A large population, for starters. The list looked at 65 cities with populations of more than 1 million. But more importantly, it aims to measure how much sway a city has over what happens beyond its own borders."
Joel Kotkin argues against size as an wise indicator of success. "Bigger might no longer mean better," he writes. "The most advantaged city of the future could well turn out to be a much smaller one. Cities today are expanding at an unparalleled rate when it comes to size, but wealth, power, and general well-being lag behind. With the exception of Los Angeles, New York, and Tokyo, most cities of 10 million or more are relatively poor, with a low standard of living and little strategic influence."