Policies are the product of cultural values, history, and politics, and where cultural values, histories, and political habits, institutions, principles, priorities, and challenges differ, policies are likely to differ as well. Policy also is influenced by the available repertoire of international policy instruments, models, and norms. Through international exchange, global governance, and, sometimes, through modeling, incentives, or peer pressure, policies internal to a nation may change. One government may adopt policy instruments from another or governments may be subject to policy convergence, appearing more alike over time. Policymakers and researchers are interested in detailing and understanding the diversity of policies as a matter of curiosity or natural history, but comparing policies also can be useful to building more exact and more nuanced understandings about how they work. Understanding how different cultural policies and cultural policy systems arise helps to explain why some governments seem to consider culture integral to their work while others view culture as a marginal concern or why some governments have developed notable policy innovations. Comparison also can help to provide context when testing the efficacy of an instrument or evaluating the strengths and weaknesses of a system (see Belfiore 2004b). Further, comparison is essential in the development of norms.