Abstract: A large number of studies have shown that technological innovation is an important source of economic growth in a nation, which can promote economic transformation and social development. The enterprise is an important subject of technological innovation. However, due to the characteristics of high risk and positive externality of technological innovation, the government is in urgent need of formulating fiscal and tax policies to stimulate it. Tax preference is an important policy tool for governments of various countries to stimulate enterprises’ technological innovation. The preferential tax policies adopted by the Chinese government to encourage enterprises’ technological innovation mainly include the 15% nominal tax rate of enterprise income tax for high-tech enterprises. Compared with the 25% statutory tax rate, the cut of 10% nominal tax rate can bring a lot of tax preferential benefits to enterprises. To be recognized as a high-tech enterprise, an enterprise must meet a series of preconditions such as the proportion of technical personnel and the proportion of R&D expenditure. Therefore, tax preferential policies can guide enterprises to increase the input of human and financial resources in technological innovation, and it has an incentive effect on enterprises’ technological innovation activities in theory.
However, the academic research conclusions on the incentive effect of tax preference on enterprise technological innovation are inconsistent, mainly because the implementation effect of tax preference is restricted by objective factors such as equity structure. If the ownership structure is regarded as the threshold variable, then the incentive effect of tax preference on enterprises’ technological innovation behavior will vary greatly under different ownership structure conditions. This paper mainly examines the ownership structure of enterprises from the two aspects of "quality" and "quantity". The "quality" mainly reflects the nature of equity structure characteristics. There are a large number of state-owned enterprises in China’s listed companies, and in recent years, many listed companies began to implement the management equity incentive to reduce the agency cost of enterprises, so the proportion of state-owned shares and the proportion of management shares have an important impact on enterprise technological innovation behavior. The "quantity" mainly reflects the quantitative characteristics of enterprise ownership structure. The higher the degree of ownership concentration, the greater the influence of major shareholders on the decision-making of enterprise technological innovation behavior.
In the existing research, some kinds of literature have discussed the marginal impact of ownership structure on the implementation effect of tax preference policies for technological innovation. The research method is mainly to add the interactive term of tax preference and ownership structure into the multiple regression model. However, the theoretical analysis in this paper shows that the actual effect of tax preference policies may not be single under different ownership structure conditions, and the research method of interaction term ignores the threshold effect of tax preference policies under different ownership structure. Therefore, to verify the research hypothesis, three econometric models are proposed in this paper: multiple regression model not considering interaction terms, multiple regression model considering interaction terms, and panel data threshold effect model. Compared with the traditional multiple linear regression model, the advantages of the panel data threshold effect model are 1.The nonlinear form of the model is not given in advance, and the threshold value and threshold quantity are determined by the endogenous sample, to avoid the subjective arbitrariness of the research conclusion caused by the artificial threshold value. 2.The significance of threshold value can be tested by the self-sampling method. In the model in this paper, the explanatory variable is R&D expenditureRd, which is calculated by dividing R&D expenditure to operating income. The explanatory variable tax preference Taxpre is measured by "Taxpre= Statutory tax rate - Nominal tax rate" proposed by Xiaozhen Pan and Fengxi Pang, in which the statutory tax rate is 25% and the nominal tax rate is the actual corporate income tax rate.
The results show that there are thresholds for the incentive effect of tax preference on technological innovation. The threshold value of the proportion of state-owned shares is 11.13%. When the proportion of state-owned shares is lower than the threshold value, tax preference can effectively promote enterprises’ technological innovation activities. When the proportion of state-owned shares is higher than the threshold value, tax preference is not conducive to enterprises’ technological innovation activities. The threshold value for the proportion of management shareholding is 17.78%. When the proportion of management shareholding is lower than or equal to the threshold value, tax preference has no impact on enterprise technological innovation. When the proportion of management shareholding is higher than the threshold value, tax preference can effectively encourage enterprises to carry out technological innovation activities. The threshold value of ownership concentration is 34.60%. When the ownership concentration is lower than or equal to the threshold value, tax preference can effectively promote enterprise technological innovation activities. When the ownership concentration is higher than the threshold value, tax preference has no impact on enterprise technological innovation.
According to the above research conclusions, the policy suggestions of this paper is that, based on the important strategic position of technological innovation in promoting national development, the Chinese government must continue to implement and improve the current tax preference policies for high-tech enterprises. However, in the process of policy implementation, we should pay attention to the threshold effect of tax preference policies. With a certain proportion of state-owned shares, proportion of management shares and degree of ownership concentration, it is difficult for the tax preference policy of technological innovation to exert its due policy effect. Therefore, in the continuous improvement of tax preference policies for high-tech enterprises, it is necessary to further clarify and optimize the preconditions for enterprises to enjoy tax preference policies, properly consider the threshold effect caused by the difference in ownership structure, and ensure that the theoretical effect of tax preferential policies can be truly realized.

Key words: tax preference, technological innovation, threshold, ownership structure