Is it really a city/suburb thing, or does it have more to do with the age of the neighborhood and its history (housing prices, appeal to various SES groups)? A newly developed neighborhood may be more SES-homogeneous, except for the subsidized lower income housing units when such are included, based on the price range of the housing offered therein. An older neighborhood where housing prices and the nature of the local economy have changed over the decades may be more SES-diverse, but with a correlation to the residents’ age and length of time living there. I.e. an area that was once a middle-income blue-collar neighborhood may now be an upper-income white-collar neighborhood, so it may have older middle-income blue-collar residents mixed with younger upper-income white-collar residents.