As always then, it raises the question 'why is it so'?

One wonders if it is the effect of densely populous living. New York would have to be the most densely populous city (as far as I know anyway), so hence, the most pronounced effect of this type (just hypothesizing here).

But that raises the issue of other examples of dense population, outside the USA - Tokyo comes to mind (other Japanese cities too I think). I'm not sure if a similar phenomena exists in Tokyo but if it does I've seen no evidence of it online - and I do deal with quite a lot of Japanese people - they are among the most courteous and respectful individuals you'll ever meet. But perhaps that could be cultural values overriding the effect of the dense population.

Interesting - I'm sure someone would have done a Ph.D on it somewhere.