Population of the Five Boroughs

I saw a graph showing the population of the Five Boroughs: Manhattan, Bronx, Staten Island, Brooklyn, and Queens. I tracked the data to: NYC Population and NYC 2008 Population.
What I was surprised about is how the population of Manhattan has actually dropped over the years:

Of course, it’s density that matters! Here’s the population expressed as 1000 people per square mile

Wow! 72,000 people per square mile in Manhattan.