Book excerpt: While governmental policies and institutions may remain more or less the same for years, they can also change suddenly and unpredictably in response to new political agendas and crises. What causes stability or change in the political system? What role do political institutions play in this process? To investigate these questions, Policy Dynamics draws on the most extensive data set yet compiled for public policy issues in the United States. Spanning the past half-century, these data make it possible to trace policies and legislation, public and media attention to them, and governmental decisions over time and across institutions. Some chapters analyze particular policy areas, such as health care, national security, and immigration, while others focus on institutional questions such as congressional procedures and agendas and the differing responses by Congress and the Supreme Court to new issues. Policy Dynamics presents a radical vision of how the federal government evolves in response to new challenges-and the research tools that others may use to critique or extend that vision.