Why do people in some societies tend to follow rules and obey the laws more than those in other societies? Is the difference institutional, or is 'culture' a better explanation? These are the central questions confronted in this book. This study explores these questions through a large laboratory experimental study which examined tax compliance behaviour in four countries: Sweden, Italy, Britain and the United States. We present what we call a 'Reasonable Choice Approach' demonstrating that most people are motivated to comply with social rules when the rules are clear, coherent, and consistent. This theory argues that most people are both rationally self-interested and social animals who have strong desires to behave according to the norms of their societies. Willing to Pay? demonstrates how institutions can shape individual behaviours and thereby help explain why social behaviours are so different across societies.