We evaluate a recent U.S. initiative to include the social cost of carbon (SCC) in regulatory decisions. To our knowledge, this paper provides the first systematic test of the extent to which applying the SCC has affected national policy. We examine all economically significant federal regulations since 2008, and obtain an unexpected result: putting a value on changes in carbon dioxide emissions does not generally affect the ranking of the preferred policy compared with the status quo. Overall, we find little evidence that using the social cost of carbon has mattered for the actual choice of policy in the U.S. This is true even for policies explicitly aimed at reducing carbon dioxide emissions. We offer an explanation related to the political economy of regulation.