老留中留大多数还是上中产，也就是家庭收入是当地的Top 15%，中西部二十多万达标，东西两岸要三十多万了。

"Sociologists Dennis Gilbert (sociologist), Willam Thompson and Joseph Hickey estimate the upper middle class to constitute roughly 15% of the population"

https://en.wikipedia.org/wiki/Upper_middle_class_in_the_United_States?