This data is not very current but,
a quick look at the name and address list of my high school graduating class, as of June 2007, shows about half of the class still in the New York area, including Westchester, Jersey and Long Island, with the rest dispersed around the country. This is of the ones who responded to a questionnaire about the class for our 40th reunion.
I went to a wedding in May. The wedding of the son of my two friends from the Bronx. They moved to New Jersey and raised their sons there. Now one son lives on the East Side and the other is in Bensonhurst.
My sister and I grew up in the Bronx, she lives in Queens and I live in North Carolina.
You really can’t get very specific about this. New York has attracted young people since the 1660’s.