For helpful comments, we thank Ben Bushong, Katherine Coffman, Sendhil Mullainathan, Paul Novosad, Suproteem Sarkar, Andrei Shleifer, Adi Sunderam, Dmitry Taubinsky, and Hans-Joachim Voth, and participants at various seminars and conferences. We thank Isabel Galea, Alex Philip, and Julia Schwed for outstanding research assistance.