“although the US population and hence the population density rose about 10 percent over the course of the naughties, the average American was living in a somewhat less dense neighborhood in 2010 than in 2000, as population spread out within metropolitan areas. If you like, we’re becoming a bit less a nation of Bostons and a bit more a nation of Houstons.

“The density of the population and the buildings make for a unique testing ground for the new kind of infrastructure we’re developing - the low carbon, resource efficient approaches to heating and power generation, transport and waste management. They all work best if done where the demand is greatest, and that means at the city scale.

“The conventional wisdom used to be that creating a strong economy came first, and that increased population and a higher quality of life would follow. The converse now seems more likely: creating a higher quality of life is the first step to attracting new residents and jobs.

“Fifty metropolitan areas are expected to have growth rates of 3 percent or more, led by Austin, Texas, and Houston. More than 100 areas are expected to see growth of 2 percent or more, including Phoenix, Denver, Boston and San Francisco, according to the report.

“A new report from the McKinsey Global Institute, Urban world: Cities and the rise of the consuming class, finds that the 600 cities making the largest contribution to a higher global GDP—the City 600—will generate nearly 65 percent of world economic growth by 2025. However, the most dramatic story within the City 600 involves just over 440 cities in emerging economies; by 2025, the Emerging 440 will account for close to half of overall growth.

“One of the major trends I’ve outlined is this movement of entrepreneurs (and as a lagging indicator venture funds) to more urban environments.