One summer in the 1950s, when I was an undergrad at the University of California at Berkeley, I took trains and hitchhiked across much of Western Europe and parts of North Africa. Barely a decade after World War II, I saw millions of people living in deplorable conditions, barely surviving. It was a shock. I never realized how difficult life was for so many. Those searing images stayed with me. In time they exerted a pull toward what is now my life’s work and loomed, distressingly and often, as I worked on An Accident of Geography.