theincidentaleconomist.com). They estimated the life expectancy for each of the USA’s 3147 independent cities and counties. Manhattan’s life expectancy rose 10 years between 1987 and 2009, the largest increase of any county, and the other four counties that make up New York City were all in the top percentile.
And the research company "InSites Consulting" reported "that American youth find New York (49%) to be the coolest city in the world, ahead of London (33%), Tokyo (32%), Paris (32%), and LA (26%)" (marketingcharts.com). New York is seen as even more cool in countries such as Germany (53%), Sweden (53%), France (53%), and Spain (54%), though the Danish (60%) and Italians (66%) are far and away the most impressed.
The city isn´t just the leading financial center in the world, the place also is a hub for fashion, advertising, media and even an uprising center for Internet technology, nicknamed Silicon Alley (wikipedia). This makes the place to a huge cluster of wealth which attracts many people - a kind of snowball effect.
New York City is by far younger than London, Paris or other European metropolises, but many parts are more than 150 years old. That is old enough to develop some patina & culture which makes a city more charming, especially neighbourhoods like the Lower East Side, Soho, Chelsea or the East Village in Manhattan. Maybe the pleasure of living in this city contributes to the rising life expectancy.