No more 9-to-5, dead-after-dusk neighborhoods. People are moving where they work, according to Paul Levy, CEO of Philly's Center City District. This week at the International Downtown Association World Congress and 59th Annual Conference in NYC, he debuted a report he wrote for the IDA. From 2000 to 2010, the population of the 10 largest urban live/work areas grew twice as fast (17.2%) as the national rate (9.7%). And 12.9 million people, 4.2% of the population, live within one mile of the country's 231 major employment centers (downtowns and town centers, office and research parks, and districts anchored by education, healthcare, and research campuses).

According to the report, Downtown Miami has a "high live-work quotient," with 23.9% of residents who live within a mile of downtown also working within a mile of downtown. (Midtown Manhattan tops that category at 55.9%.) All together, Miami's population within a mile of downtown is about 140,800, and there are about 52 jobs per acre in the downtown area--less than intense urban agglomerations like Midtown Manhattan, but more than most US cities.