## 5 Discussion
### Analysis of Spatial Spillover Effect  
In order to analyze the spillover effect of GPSTPS policy on regional S&T innovation ability more comprehensively, this paper adopts a partial differential method to analyze the direct and indirect effect of spatial spillover. Based on the SDM, the current research explores the direct and indirect effects of S&T innovation ability in the central, western and eastern regions. The results are shown in Table 8. Direct effect analysis can reflect the impact of GPSTPS policy on the local S&T innovation ability, while indirect effect analysis reflects the impact of GPSTPS policy on the adjacent regions' S&T innovation ability.  
(1) Eastern region  
In the direct effect, the coefficient of GPSTPS policy is 1.046, which is significant at the level of 5%. The result indicates that, in the eastern region, GPSTPS policy has a positive effect on promoting the local S&T innovation ability. The larger the PMC index, the higher the feasibility and rationality of GPSTPS policy. A sound and comprehensive GPSTPS policy can improve the quality of S&T public services. The role of S&T public services in promoting regional S&T innovation is described in Section 5.2. In the indirect effect, the coefficient of GPSTPS policy is positive and significant, indicating that the GPSTPS policy has a positive spatial spillover effect on the neighboring provinces' S&T innovation ability. The possible reason is that in order to strengthen the communication and narrow the differences between provinces, local governments often implement the same policy in areas with similar economic development, which is also known as policy diffusion in the field of policy science. Therefore, based on the geographical distance spatial weight matrix, the adjacent provinces in the eastern region often adopt the same GPSTPS policy, which promotes the local S&T innovation ability.  
(2) Central and western regions  
It can be seen from Table 8 that the coefficients of GPSTPS policy in the direct effect in the central and western regions are both positive, but they are not significant. The results indicate that GPSTPS policy in central and western regions has a positive role in promoting the local S&T innovation ability, while the effect is not obvious. The possible reasons for the insignificant effect in the central and western region are concluded as follows. S&T public services are highly specialized. However, in the central and western regions, especially the western regions, one of the regional characteristics is the poor infrastructure and there are few producers who supply S&T public services. This means that the purchase objects in GPSTPS are relatively lacking, which restricts the implementation of the GPSTPS policy and hinders the improvement of local S&T innovation ability. Furthermore, the indirect effects in the central and western regions are also positive and nonsignificant. The result indicates that the spatial spillover effect of GPSTPS policy on the improvement of adjacent provinces' S&T innovation ability is not obvious in the central and western regions. The  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multirow{2}{*}{**Variable**} & **Direct Effect** & **Indirect Effect** & **Total Effect** \\  & & **(S\&T** & **(S\&T** \\)** & **Innovation** & **Innovation** & **Innovation** \\  & & **Ability)** & **Ability)** \\ \hline Eastern region & pol & 1.046 ** & 1.421 ** & 2.467 \\ Central region & pol & 0.451 & 0.653 & 1.104 \\ Western region & pol & 0.652 & 0.711 & 1.363 \\ \hline \hline \end{tabular} Note: ** means that the corresponding variables are significant at the level of 5%.  
\end{table}
Table 8: Direct and indirect effects of SDM.  
possible reason for the results may be the imperfect policy system, and the unsound policy cannot influence on the other regions' S&T innovation ability.