Project Syndicate linked to this (2011) McKinsey study of urban contribution to world GDP. The top bullet-point take-away: “only 600 urban centers generate about 60 percent of global GDP.” Yet, because cities, as nodes in a global economic network, are distributed by a power law, any picture drawn by the top 600 urban centers tends to strongly de-dramatize the reality.
Wikipedia has a helpful table of world cities with a variety of GDP estimates. (The Brookings Institute figures are the most complete, and also the most generous.) From these it can be seen that Tokyo, on its own, accounts for almost 2% of world GDP. The world’s 10 most productive cities — Chicago, London, Los Angeles, Moscow, New York, Osaka/Kobe, Paris, Seoul, Shanghai, and Tokyo — account for roughly 10% of total global economic output between them. The next thirty cities together do not quite double this figure, and from then on, the contribution of each city added dwindles rapidly.
McKinsey estimates the economic weight of the world’s “23 megacities — with populations of 10 million or more” somewhat more modestly, at 14% of global GDP. It expects them to contribute no more than 10% of global growth through to 2025, while: “In contrast, 577 middleweights — cities with populations of between 150,000 and 10 million, are seen contributing more than half of global growth to 2025, gaining share from today’s megacities. By 2025, 13 middleweights are likely to be have become megacities, 12 of which are in emerging-markets (the exception is Chicago) and seven in China alone.”
UF anticipates that the combination of continued urban agglomeration and economic concentration will tend to steepen the distribution, but the secular shift of economic gravity from West to East will dampen this pattern in the short-medium term. If, by mid-century, there is not a single Chinese economic center accounting for more than 3% of total global economic production, all our expectations about the world will have been proven wrong.
ADDED: A mid-century prediction isn’t very audacious, but it’s timidity is drawn from an important pattern of change. The world’s two most productive cities, by far, are Tokyo and New York, and both are likely to see their relative contribution to global GDP shrink substantially over coming decades. In consequence, the near-term shifts in the distribution of economic activity will appear as a dilution, until a new ‘capital’ of world commerce emerges — in a process that can be expected to take at least 20 years.