So now we know the ideology of every clerk’s justice in every year back to 1937 — the first year for which the Martin-Quinn scores are calculated. We can now calculate that Columbia grads tend to clerk for justices of this ideological type, and Stanford grads for that type, and so on. And while we’re not measuring clerk ideology directly, there is strong evidence that, for better or worse, justices prefer clerks with ideologies similar to their own. Clarence Thomas has said: “I won’t hire clerks who have profound disagreements with me. It’s like trying to train a pig. It wastes your time, and it aggravates the pig.”
Caution as the number of clerk-justice pairings are small after Harvard, Yale and Columbia.