Research On The Herd Effect Of Stock Market Under The Condition Of Heterogeneous Individuals

In June 2015,China's stock market experienced an unprecedented "stock disaster".Part of the reason for the "stock disaster" is the herding behavior of investors.Herd behavior does more harm than good to the stock market.How to properly reduce the herd behavior of investors is a long road and requires the joint efforts of investors and regulators.In this paper,we will study the sheep phenomenon in the stock market from the perspective of information diffusion based on scale-free network model and investors' own game,and provide suggestions for investors to better adapt to the change of market.The main research contents of this paper are as follows:Firstly,this paper will build a scale-free network model,and then use the improved infectious disease model to simulate the process of information dissemination,in order to analyze the path of the stock market information diffusion and its influencing factors.While constructing scale-free network,the network nodes are divided into "expert" group and "ordinary" group.Through the numerical simulation,we get the information diffusion evolution graph,so as to analyze the influence of each variable on information diffusion in the process of information diffusion.Secondly,we use the evolutionary game model based on heterogeneous individuals to study the game process of small and medium-sized investors.In the stock market,each person's investment ability and learning ability are different.The difference in investment ability and learning ability will affect the investor's strategic choice.Therefore,in this paper,it is considered that the individual in the game group has heterogeneity,and the heterogeneity is reflected in the strategy space of the game players: the investors with stronger investment ability and learning ability have larger strategic spaces.And in contrast,the strategy space of investors with poor investment ability and learning ability is limited.Even if they know a certain strategy is better,they can't succeed in imitating or learning this better strategy because of their limited ability.Based on this point of view,this paper uses evolutionary game theory under the condition of heterogeneous individuals to construct a heterogeneous evolutionary game system to analyze the process of investors' game and to carry out numerical simulation.Through the study of the improved infectious disease model,it is found that: There are two inflection points in the speed of information diffusion in the stock market.By changing the effective transmission rate and immunity rate,the information interference degree of the system and the speed of information diffusion can be changed.Moreover,the influence of "experts" on information diffusion is significantly greater than that of "ordinary" groups.The effective transmission rate of "experts" and the increase of the number of "experts" can accelerate the speed of information dissemination,facilitate the spread of information in the system and promote the influence of the system.By studying the evolutionary game model based on heterogeneous individuals,we find that: The stronger the investor's ability and learning ability is,the more investors will have complete strategic space.With the increasing investment ability of investors in the whole system,the proportion of investors who adopt independent analysis strategy in the system will continue to rise and lead to less herd effect.On the contrary,the lower the proportion of individuals with strong investment ability and learning ability,the more obvious the herd effect is.It indicates that the herding effect in the stock market is controllable to a certain extent,which is closely related to the investment ability and learning level of investors.The innovation of this paper is mainly in two aspects:(1)At present,there are few researches on evolutionary securities in China.In this paper,we will analyze the evolutionary game system of investors,and provides a basis for future research on the evolution of securities science.(2)Traditional evolutionary game theory assumes that all individuals are homogeneous,and there is no distinction between individual differences,which has some limitations.This paper adds heterogeneity to the evolution model.Based on the evolutionary game model of heterogeneous individuals,the small and medium investors in the stock market are regarded as the evolutionary game system,and the differences of individual investment ability and learning level are taken into consideration.By analyzing the strategy selection of small and medium investors,the herd phenomenon of the stock market is studied.(3)While constructing the information dissemination model of the stock market,it distinguishes the "expert" group and the "ordinary" group,which embodies the heterogeneity and has a certain innovation.It and can better analyze the influence factors of the information diffusion.