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.
cough cough the Bay Area. Seriously, though, the Santa Clara County metropolitan statistical area clocks in at 0.45 while New York is 0.60 [1].
[1] https://www.census.gov/prod/2012pubs/acsbr10-18.pdf