Policy analysis with incredible certitude

"Analyses of public policy regularly express certitude about the consequences of alternative policy choices. Yet policy predictions often are fragile, with conclusions resting on critical unsupported assumptions. Then the certitude of policy analysis is not credible. This paper develops a typology of incredible analytical practices and gives illustrative cases. I call these practices conventional certitudes, dueling certitudes, conflating science and advocacy, and wishful extrapolation. I contrast these practices with my vision for credible policy analysis"--National Bureau of Economic Research web site.