On the basis of the government subsidies for renewable energy electricity, this study builds a two‐stage duopoly model in an industry with a renewable electricity enterprise and a conventional electricity enterprise in the market. Under the assumption of the generalised social welfare maximisation authority, this study discusses the effects of three types of government subsidies, business fixed input subsidy, output subsidy and mixed subsidy. First, the mixed subsidy policy is the best one under generalised social welfare. However, when the cost of renewable energy production or the energy negative coefficient is low, this subsidy policy generates a high electricity price. Second, when the output subsidy is used, the optimal price and optimal output of renewable energy will decrease with the increase of production cost and negative externality coefficient of renewable energy enterprises. Finally, both the optimal price and optimal outputs depend on the level of negative externality and the cost of renewable energy production.

The problem of fraud in China's health insurance has existed for a long time and is becoming more serious, which needs to be solved urgently. This article constructs a tripartite evolutionary game model to study the formation mechanism of the Health Insurance fraud, game participants including medical administrative organization (MAO, a government department responsible for health insurance supervision), medical institutions (MI, such as hospitals), and insured individuals (II, who participating in medical and healthcare insurance). By analyzing the equilibrium of the tripartite evolutionary game, this paper makes an in-depth study on the formation and resolution of health insurance fraud. The results show that: (1) How to prevent the fraud behavior of the medical institutions is the difficulty and core of the problem. It is necessary to achieve effective supervision of the MAO, improve the internal management of the MI and give play to the supervisory role of the II. (2) The regulatory behavior of the MAO needs to focus on protecting the interests of the II, not only to encourage them to actively play the role of supervision and reporting but also to prevent their collusion with MI. (3) On the one hand, the MAO needs to strengthen supervision and increase the punishment for fraud. On the other hand, they also need to take incentive measures to guide all subjects to form a sound internal management mechanism.