For decades, administrations of both political parties have used cost-benefit analysis to evaluate and improve federal policy in a variety of areas, including health and the environment. Today, this model is under grave threat.In Reviving Rationality, Michael Livermore and Richard Revesz explain how Donald Trump has destabilized the decades-long bipartisan consensus that federal agencies must base their decisions on evidence, expertise, and analysis. Administrative agencies are charged by law with protecting values like stable financial markets and clean air. Their decisions often have profound consequences, affecting everything from the safety of workplaces to access to the dream of home ownership. Under the Trump administration, agencies have been hampered in their ability to advance these missions by the conflicting ideological whims of a changing cast of political appointees and overwhelming pressure from well-connected interest groups. Inconvenient evidence has been ignored, experts have been sidelined, and analysis has been used to obscure facts, rather than inform the public. The results are grim: incoherent policy, social division, defeats in court, a demoralized federal workforce, and a loss of faith in government's ability to respond to pressing problems.This experiment in abandoning the norms of good governance has been a disaster. Reviving Rationality explains how and why our government has abandoned rationality in recent years, and why it is so important for future administrations to restore rigorous cost-benefit analysis if we are to return to a policymaking approach that effectively tackles the most pressing problems of our era.