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Cost-benefit analysis has been criticized on numerous grounds. It is common in such analyses to treat undesirable side effects (including risks) as external or social costs and to quantify these costs insofar as possible. In this paper I take the view that both desired effects (benefits) and undesired effects (malefits) are outputs of the technology. Costs are the dollars paid for the mixture of benefits and malefits actually produced. It is a futile and often misleading exercise to attempt to quantify the value of the net output of a public-service technology. A social-political decision must be taken as to whether or not the total output is worth the cost. If citizens are to participate usefully in such a decision, they need to understand the nature of this total output. Dollar-quantification of ``benefits'' and ``external costs'' obscures the actual physical-social effects of the technology. Cost-benefit analysis is a better tool for advocacy in technological decisions than for informing the public. By focusing attention on formulas and numbers, the analysis seems to substitute scientific reasoning for the painful process of making value judgments. But the value judgments are always present; they can be concealed but not escaped. Technological decisions are more political than scientific.