He’s written a book on the topic, but the following Thomas Sowell quote about intellectuals’ poor accuracy rate comes from the new essay collection Dismantling America

How have intellectuals managed to be so wrong, so often? By thinking that because they are knowledgeable ? or even expert ? within some narrow band out of the vast spectrum of human concerns, that makes them wise guides to the masses and to the rulers of the nation.

But the ignorance of Ph.D.s is still ignorance, and high-IQ groupthink is still groupthink, which is the antithesis of real thinking.