More than 1.5 billion people live in countries affected by violent conflict. The World Development Report 2011: Conflict, Security, and Development examines the changing nature of violence in the 21st century, and underlines the negative impact of repeated cycles of violence on a country or region’s development prospects. Preventing violence and building peaceful states that respond to the aspirations of their citizens requires strong leadership and concerted national and international efforts. The Report is based on new research, case studies and extensive consultations with leaders and development practitioners throughout the world.