This lesson describes how a government decides whether and how much it should spend on vulnerability reduction. There are techniques and methods by which decision-makers compare development alternatives. The differences between the risk that a potentially catastrophic event will occur and uncertainty are described, with uncertainty providing greater difficulty in economic analyses. There is a range of methods for identifying the complex mix of competing costs and benefits associated with any restructuring of investment priorities to accomplish disaster mitigation. The possibilities are described in terms of the opportunity costs and present value. Impact and consequent losses include: (1) direct monetary effects; (2) indirect monetary effects; (3) direct, non-monetary effects; (4) indirect, non-monetary effects; and (5) loss of non-renewable natural resources. The difficulties in assigning values to these effects are described, as well as the means of judging the costeffectiveness of such interventions. An advantage of screening projects using a framework of analytical methods is that it can assist in focusing on a variety of possible outcomes and make the factors influencing these outcomes quite explicit.