On a number of subjects—not just segregation—I note that the public opinion of California in 2008 is quite similar to the public opinion of Stanford in 1963.
This is easy to explain: in post-1945 America, the source of all new ideas is the university. Ideas check out of the university, but they hardly ever check in. Thence, they flow outward to the other arms of the educational system as a whole: the mainstream media and the public schools. Eventually they become our old friend, "public opinion". This process is slow, happening on a generational scale, and thus the forty-five-year lag.

A gentle introduction to Unqualified Reservations (part 1)