ORLANDO—For commercial real estate developers,urbanization is the new black. Of course, it's not urbanization forurbanization's sake. Savvy developers are following—andfueling—this trend.

For decades, most Americans settled in the suburbs. Now, there'sa mass exodus—or at least a growing movement—toward urban cores.According to Census Bureau data, American cities are witnessing arenaissance, of sorts, as residents migrate to downtown areas.

In 2013, 2.3 million more people were living in metro areas thanin 2012, the Census Bureau reports. All told, 269.9 million peopleare living in and around cities. The population shift started in2010, igniting a rate of urban growth that reverses thecentury-long norm. In fact, McKinsey & Co.'sresearch concludes that the speed and scale of urban expansion isunprecedented and growing cities could inject up to $30 trillion ayear into the world economy by 2025.