Meet The Mega Region

You've undoubtedly heard of the mega-city, especially if you are a regular reader. Now, faithful reader, I introduce you to the mega-region.

Mega-regions are integrated sets of cities and their surrounding suburban hinterlands across which labor and capital can be reallocated at very low cost. The 40 that we will identify here all have economies on the scale of $100 billion or more. Similarly, the 40th largest nation in terms of GDP also has an economy of about $100 billion.
The mega-regions of today perform functions that are somewhat similar to those of the great cities of the past - massing together talent, productive capability, innovation and markets. But they do this on a far larger scale. Furthermore, while cities in the past were part of national systems, globalization has exposed them to world-wide competition. As the distribution of economic activity has gone global, the city-system has also become global - meaning that cities compete now on a global terrain. Urban mega-regions are coming to relate to the global economy in much the same way that metropolitan regions relate to national economies.
Unlike mega-cities, which are termed as such simply for the size of their populations, mega-regions are by definition places that claim large populations, large markets, significant economic capacity, substantial innovative activity, and highly skilled talent.
If we take the largest mega-regions in terms of population, the world's 10 biggest are home to roughly 666 million people or 10.5 percent of world population; the top 20 comprise close to 1.1 billion people, 17 percent of the world total; while the top 40 are home to 1.5 billion people, 23 percent of global population.

- Richard Florida, Who's Your City? : How the Creative Economy Is Making Where to Live the Most Important Decision of Your Life