在A-level经济学中，关于政府干预这一大内容有许多知识点，下面就是关于政府干预的知识内容所做的提炼与总结。
Market failure 市场失灵
Market failure occurs when the free market forces of demand and supply fail to produce the quantities of goods and services at levels which should have reflected the optimal resource allocation.
当市场并没有自动调整到资源最佳配置的状态以提供合适量的商品和服务时,我们称这种状态为'市场失灵。
Externalities 外部性;外部影响
An externality is said to arise if a third party that is not directly involved is affected by the decisions and actions.
外部性是指某项活动对不直接参与活动的第三方所造成的间接性影响。
Social cost 社会成本
Social costs are all of the related costs associated with that action
社会成本是指和某项活动相关的全部成本。
Private cost 私人成本
Private cost are costs involved in an action that accrue to the decision maker.
私人成本是指某项活动对决策者造成的成本。
Cost-benefit analysis 成本效益分析
Cost-benefit analysis is a procedure which takes into account all costs and all benefits of a project.
成本效益分析是一种将全部成本和效益都纳入考虑范围的分析过程。
记住以上的知识点内容，并能够运用到A-level考试当中去，平时的知识点积累尤其重要。
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