Manufacturing Doubt

International audience; In their persistent fight against regulation, firms have developed specic strategies to take advantage of scientific uncertainty. They have spent large amounts of money to manufacture doubt and artificially keep controversies alive. We develop a new model to study the interplay between scientific uncertainty, fifirms' communication and public policies. The government is benevolent but populist and maximizes social welfare as perceived bycitizens. The industry can provide costly evidence that its activity is not harmful. Citizens incorrectly treat the industry's information on par with scientific knowledge. We characterize the industry's optimal communication policy. We find that communication effort is non-monotonous and discontinuous in scientific belief. As scientists become increasingly convinced that the industrial activity is harmful, firms first fight harder and harder to reassure people. When scientists' beliefs reach a critical threshold, however, overcoming the scientific consensus becomes too costly and the industry stops its e¤orts abruptly. We then study the impacts of firms' communication on scientific funding. Perversely, a populist government may want to support research to better allow firms to miscommunicate. Populist policies can entail significant welfare losses. Establishing an independent funding agency always reduces these losses and may lead to under- or over- investment in research with respect to the first-best.