Coming Apart Watch
the authors calculate what they call a Residential Income Segregation Index, which comes from “adding together the share of lower-income households living in a majority lower-income tract and the share of upper-income households living in a majority upper-income tract … (The maximum possible RISI score is 200. In such a metropolitan area, 100% of lower-income and 100% of upper-income households would be situated in a census tract where a majority of households were in their same income bracket.)”
Overall, the national index rose from 32 in 1980 to 46 in 2010.
All things considered, for either year the level seems to me to be pretty low, actually. Put it this way: Suppose that you were to calculate a similar index for colleges, using the household income of the parents. I bet that you would see numbers that are much higher.