When the city of Detroit filed for bankruptcy, it became the largest such filing in United States history. Detroit's population has dropped from 1.8 million in 1950, when it was America's fifth-largest city, to less than 700,000 today. Its industrial base lies shattered.

And yet we live in a world where cities have never had it so good. More than half of the world's population is urban for the first time in history, and urban hubs generate an estimated 80 percent of global GDP. These proportions will rise even higher as emerging market economies urbanize rapidly. So, what can the world learn from Detroit's plight?

As recently as the 1990s, many experts were suggesting that technology would make cities irrelevant. It was believed that the Internet and mobile communications, then infant technologies, would make it unnecessary for people to live in crowded and expensive urban hubs. Instead, cities like New York and London have experienced sharp increases in population since 1990, after decades of decline.