Research On The Influence Of City Size And Population Density On Regional Innovation

City is the gathering place of innovative elements such as human resources,scientific and technological resources,and information resources.Innovation often occurs in cities,especially in big cities.Innovation is also the driving force and source for cities to maintain sustainable development.With the development of regional economy and the improvement of population concentration,the scale of Chinese cities is getting larger and larger,and the level of population density is also increasing.Under the new normal,it is of great significance to study the relationship between the urban scale,population density and innovation output,so as to implement the innovation driven development strategy,improve innovation ability and innovation efficiency.This paper takes urban scale and technological innovation ability as the research object.Firstly,it combs the research summary and theoretical basis of urban scale,population density and innovation output at home and abroad.It analyzes the influence mechanism of urban scale on innovation output from the aspects of agglomeration of enterprises and industries,market demand effect and so on.It also analyzes the spillover effect and social network effect of urban talent agglomeration And analyze the impact mechanism of population density on innovation output.Secondly,based on the panel data of 225 cities at prefecture level and above in 2007-2016,this paper tests the impact of city size and population density on regional innovation output.At the same time,in order to check whether there is an alternative relationship or complementary relationship between urban scale and population density,we add the cross term of urban scale and population density to the model to check whether there is an alternative relationship or complementary relationship between urban scale and population density.By replacing the main explanatory variables,dividing the samples into four regions,and removing four municipalities,the robustness of the research results is verified.Finally,considering that although the improvement of urban scale and population density will promote the improvement of urban innovation ability,the improvement effect may depend on the development of urban scale and population density to a certain extent to have a significant impact,that is,there may be a "threshold effect" on the improvement effect of innovation ability of urban scale and population density.Therefore,this study takes the city size and population density as threshold variables,and uses bootstrap method to repeatedly sample 500 times to test the threshold effect of explanatory variables.The main conclusions are as follows:Firstly,the panel model results show that the urban scale and population density have a significant positive effect on innovation output at the level of 1%,and the control variables such as R&D input,the proportion of tertiary industry and infrastructure also have a significant impact on regional innovation output,while the impact of international direct investment on regional innovation output is not significant.The above results are robust.Secondly,there is a positive interaction between urban size and population density.The multiplier of urban size and population density is significantly positive.It shows that the impact of urban scale and population density on innovation output is interdependent,and the contribution is interactive.There is a significant positive interaction between them.One factor should play its role under the condition of another factor.Thirdly,the empirical results of the threshold panel model show that there are threshold effects on the impact of urban size and population density on innovation output.There is a single threshold effect in urban scale.When the urban scale exceeds the threshold of 2.217 million people,the innovation promotion effect of urban scale expansion increases significantly.Only when the urban scale exceeds a certain threshold,can a city have perfect information,communication and other infrastructure,and its innovation resource agglomeration effect,human capital accumulation effect,information exchange network formation effect and transaction effect Only when the rate is raised can the effect be effectively exerted and the city become the center of innovation and invention.There is a double threshold effect in population density.Further research finds that for low-density cities and medium-density cities,the increase of urban population density has a significant positive impact on urban innovation ability;but in high-density cities,the increase of population density does not have a significant impact on innovation output,which shows that the employment concentration density of some cities in China is too high,which has appeared significant The agglomeration of is uneconomical.According to the results of empirical analysis,the paper puts forward relevant countermeasures and suggestions:first,continue to grow the size of large cities,especially small and medium-sized cities;second,actively improve the population density of cities while increasing the size of cities;third,integrate smart growth theory and compact city concept into urban planning and development concept.Fourth,promote the dislocation development between cities through the strategy of urban agglomerations.Finally,it points out the shortcomings of this study.