According to a new study by economists at the University of California, Berkeley and the Paris School of Economics at Oxford University, the wealth gap between the top one percent of earners and the rest of the population is the widest it’s been in nearly 100 years. Paul Pierson, a professor of political science at the University of California at Berkeley and co-author of Winner Take All Politics: How Washington Made the Rich Richer and Turned Its Back on the Middle Class, takes apart the numbers and explains what sorts of policies have led to the growing disparity.