Population Drop in New York?

Question

Why did New York's population dropped in 1960-2000?(i need like websites where i can find this information)

Answer 1

1 - Many people living in the City moved to suburbs and into Connecticut and New Jersey. The tax base started dwindling and that made more people leave

2 - during this period many companies moved out of the City as well, mainly because of costs.

3 - during each rececession, NYC loses about 100,000 just due to Wall Street layoffs

Here is 1980 to 2000
http://www.nyc.gov/html/dot/downloads/pdf/ci_demographics.pdf