Social scientists often argue that we can explain variation in mass violence by focusing on the strength or weakness of state institutions. Neil Smelser's research on England, Mexico, and the United States in the 18th and 19th centuries, for example, finds that periods in which police corruption was rife, training and equipment were poor, and local political interference high were invariably accompanied by large increases in riots. James Tong's study of violence in Ming China found that riots occurred most often in peripheral areas where the effectiveness of the Chinese state was weakest. More recently, studies of collective mobilization and violence in places as diverse as Los Angeles, the former Soviet Union, and the former state of Yugoslavia have identified state capacity, and the impact it has on individuals' decision about whether to participate in violence, as a crucial factor in determining where and when violence takes place. DiPasquale and Glaeser, for example, draw on standard economic price theory to explain the 1992 Los Angeles riots, concluding that rioting was greatest in those places where the financial gains were highest, and the state's capacity to punish individual rioters weakest.