摘要：Cost–benefit analysis is often used by governments and other organizations, such as private sector businesses, to evaluate the desirability of a given policy. It is an analysis of the expected balance of benefits and costs, including an account of foregone alternatives. Cost – benefic analysis helps predict whether the benefits of a policy outweigh its costs, and by how much relative to other alternatives. Cost -Benefit analysis can be considered simply rational decision-making. People use it every day and it is older than written history. Human natural grasp of costs and benefits is sometimes inadequate, however, when the alternatives are complex or the data uncertain. Then we need formal techniques to keep our thinking clear, systematic and rational. These techniques constitute a model for doing cost - benefit analysis. They include a variety of methods: identifying alternatives; defining alternatives in a way that allows fair comparison; adjusting for occurrence of costs and benefits at different times; calculating dollar values for things that are not usually expressed in dollars; coping with uncertainty in the data and summing up a complex pattern of costs and benefits to guide decision-making
关键词：cost; benefit; analysis; investment; net present value; internal rate of return
