David Brooks on how diversity within the intellectual elite is much less practiced than preached:
My favorite illustration of this latter pattern comes from the first, noncontroversial chapter of The Bell Curve. Think of your twelve closest friends, Richard J. Herrnstein and Charles Murray write. If you had chosen them randomly from the American population, the odds that half of your twelve closest friends would be college graduates would be six in a thousand. The odds that half of the twelve would have advanced degrees would be less than one in a million. Have any of your twelve closest friends graduated from Harvard, Stanford, Yale, Princeton, Caltech, MIT, Duke, Dartmouth, Cornell, Columbia, Chicago, or Brown? If you chose your friends randomly from the American population, the odds against your having four or more friends from those schools would be more than a billion to one.
UPDATE: Brad DeLong corrects these calculations here. (But the odds are still rather low.)