摆渡论文网（www.baydue.com）-专业留学生作业辅导中心英文paper写作-Externality theoryThe externality theory has been developed for more than 80 years, but it is still in a vague and chaotic state. There are three dilemmas influencing the development of externality theory: the definition of externality is unclear; The instrumental value position of externality theory is inaccurate; The perspective of externality theory, stand, value concept, fan wu is not unified. Externality theory can find its way out from the following aspects: correcting the position of externality theory; To explore new theoretical sources; Find the breakthrough of externality concept; Reposition the development direction of externality theory.For example, based on pigous welfare economics, externality theory has a history of more than 80 years, but there is no unified externality theory up to now. Different scholars have different expressions of externality theory. From the basic concept to the theoretical logic system, externality theory is still in a state of confusion, vagueness and rigidity. By analyzing the predicament of the theory, the author tries to find the way out of the theory.Inspired by Marshalls external economy, pigou founded the externality theory, which was critically developed by coase. The discussion of externalities by these three people is called the three milestones in the development of externality theory.In his principles of economics, Marshall wrote: can we distinguish the expansion of production in the economy from two types? The second type is that the expansion of production comes from the efficiency of resource organization and management of individual enterprises. We call the former external economy and the latter internal economy. This statement provides a source of thought for the formal emergence of externality theory.Inspired by Marshall, pigou formally proposed and established the externality theory. Pigou believed that in economic activities, externalities exist if certain firms cause losses to other firms or to society as a whole without cost. In pigou, externality can be divided into external economy and external uneconomy, while external economy can negatively affect the economy. Something had to be done about it, and after an examination he found a way to tax and subsidize it. Thus the externality theory can be constructed from the problem to the concept to the theoretical logic to solve the problem.The essence of those problems mentioned by pigou, coase argues, is the reciprocity of the effects of aggression. Under this assumption, to solve or avoid the effect of infringement, the first thing is to give and clarify the right of infringement. If the right is clear, the effect of infringement can be solved through the market. From the logical starting point of negating pigou, coase thoroughly criticizes the externality theory, but it is also a significant development of externality theory.When the externality theory reached coase, it basically stagnated. There are three dilemmas restricting the development of externality theory.The concept of externality is the starting point of the study of externality theory. The basic concept is not clarified or very confused, so it is imaginable that it is difficult to conduct further theoretical research.Marshall described the external economy in his principles of economics as dependent on the general prosperity of the industry. This extremely sketchy description, which John Clapham calls an empty box, argues that the real world has no counterpart to it.After pigou in the welfare economics, proposed the external economy and internal economy concept, from the point of view of logical theories, pigou external economy and internal economy with Marshalls external economy and internal economy is not corresponding, pigou refers to external economy and internal economy is not the same as Marshall refers to external economy and internal economy .Pigou externality theory based on the marginal private cost and social cost difference theory as the point of view, on the one hand it to externality concept of a relatively clear outline, on the other hand also bind external economy in a relatively narrow range, forming and Marshall external economy described in the huge differences between things. Due to the lack of sufficient persuasiveness, pigous externality concept and theory were quickly criticized and attacked by others. It is because of this point that later scholars who discuss the externality issue always try to get out of the scope of pigous externality concept and theory due to the defect of pigous externality concept and theory.Lets look at some of the most representative representations of externality from later scholars. James mead, a kind of external economy refers to an event like this: it makes a direct cause of the incident decision when there is no participation, perceive