I'm not sure what's being debated here, but I just want to point out Manhattan is less than 20% of NYC's land area. And as you point out this is only about half of Manhattan. So 10% of the total city?
The issue was comparing the City of London to half of Manhattan, for purposes of comparison. I felt like some clarity on the sizing would be helpful. I think you're correct in the 10%. Also, I should have compared Half of Manhattan to the City of London, but I couldn't find a good illustration of that. Hopefully, the links are found to be useful.
