New Yorkers are fleeing the state and city in alarming numbers -- and costing a fortune in lost tax dollars, a new study shows.

More than 1.5 million state residents left for other parts of the United States from 2000 to 2008, according to the report from the Empire Center for New York State Policy. It was the biggest out-of-state migration in the country.

The vast majority of the migrants, 1.1 million, were former residents of New York City -- meaning one out of seven city taxpayers moved out.

"The Empire State is being drained of an invaluable resource -- people," the report said.

What's worse is that the families fleeing New York are being replaced by lower-income newcomers, who consequently pay less in taxes.

Overall, the ex-New Yorkers earn about 13 percent more than those who moved into the state, the study found.

And it should be no surprise that the city -- and Manhattan in particular -- suffered the biggest loss in terms of taxable income.

The average Manhattan taxpayer who left the state earned $93,264 a year. The average newcomer to Manhattan earned only $72,726.

That's a difference of $20,538, the highest for any county in the state. Staten Island was second, with a $20,066 difference.

It all adds up to staggering loss in taxable income. During 2006-2007, the "migration flow" out of New York to other states amounted to a loss of $4.3 billion.

The study used annual US Census reports, which showed which states had increased population, combined with Internal Revenue Service data, which show which states, cities and counties had lost people.