In the United States, large cities contribute 85% of the GDP. That's right — the vast majority of economic productivity comes from cities. And this isn't just true of the US — it's also the case in China and Europe, too.
According to McKinsey Global Institute, a management consulting firm:
Large US cities, defined here as those with 150,000 or more inhabitants, generated almost 85 percent of the country’s GDP in 2010, compared with 78 percent for large cities in China and just under 65 percent for those in Western Europe during the same period. In the next 15 years, the 259 large US cities are expected to generate more than 10 percent of global GDP growth—a share bigger than that of all such cities in other developed countries combined.
So if you're wondering why we need cities, and why more people live in cities than ever before, this single statistic helps explain it all to you. Cities are the places where we generate wealth, both economically and culturally.
Read more on the McKinsey & Co. website.