New York City decline: Cities don't lure the middle class... They create it.

http://www.portfolio.com/views/blogs/market-movers/2009/02/05/new-york-city-datapoint-of-the-day?tid=true

The money quote is:

"There simply aren't middle-class job opportunities in New York any more: Of the 10 occupations that are expected to have the largest number of annual job openings in the city through 2014, only two offer median wages greater than $28,000 a year."