When is it impossible (and when is it possible) for institutions to generate a socially desirable outcome? Why do people vote and how do their motives influence who wins office? How does a jury deliberate and what affects the process through which it reaches an agreement? In this course, we will explore ideas that shed light on these questions and others by focusing on collective decision making and the effects of institutional design on policy outcomes. In the first part, we will take a formal approach to social choice theory--how individual preferences are aggregated to form a collective preference and determine a collective decision. In the second part of the course, we will discuss recent theoretical and empirical work that analyzes the interactions among individual preferences, institutions and outcomes in settings such as elections, government and courts.