老留中留大多數還是上中產，也就是家庭收入是當地的Top 15%，中西部二十多萬達標，東西兩岸要三十多萬了。

"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?