County statistics are misleading here. Santa Clara County is a big place (almost the size of Long Island) with lots of municipalities. New York County is just 1 of 5 counties that encompass New York City!

If you look at Brooklyn (Kings County), the number is 0.499, Queens County the number is 0.433.

According to another site, the citywide number was 0.547 in 2013. ( https://nextcity.org/daily/entry/inequality-new-york-city-we... )