From the NY Times:
The tally of people New York has lost to other states since 2000 is the highest it has been in three decades, but unlike the situation in the 1970s, the surplus of births over deaths has kept the population from declining.
Over all, it rose to 19.4 million from 18.9 million, according to the 2010 census.
An analysis of census data by the Empire Center for New York State Policy at the Manhattan Institute found that in the latest decade, New York gained 895,150 immigrants from abroad. The number people who left for other states outnumbered the number who arrived from other states by more than 1.5 million; it is the second consecutive decade in which domestic migration loss was the highest of any state as a percentage of population. All in all, the population declined by 675,00 as a result of migration since 2000.
Twenty other states, mostly in the Northeast and Midwest, lost more residents than they gained to domestic migration. Combining domestic and foreign migration, New York — with the third highest rate of loss — was one of 13 states that suffered a net loss.