## 4 Regression Analysis
### Estimation Results  
We confirm that almost all of the coefficients of the variables, except for the natural log of the population, have the expected sign. We briefly summarize the results in terms of the control variables. First, the coefficients of the natural log of standard financial size are statistically significant and show a positive sign for the implementation of green purchasing for most items. This result is consistent with the literature [3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13]. On the other hand, this variable has no significant impact on the measurement of green purchasing for most items. These results imply that financial constraints may not be a strong barrier to measuring the green purchasing te. Second, we find that the natural log of population has no significant impact on both the implementation of green purchasing and measuring the green purchasing rate for most items. It may not be appropriate as a proxy. The details are summarized in Table 10.  
Next, we explain the results with regard to the GPP. Table 1 summarizes the average partial effects (hereinafter, APEs) of adopting a GPP on each of the dependent variables for 21 items. Table 1 also shows the effective sample size for each estimation. This table indicates that the adoption of a GPP has positive and statistically significant impacts on both the implementation of green purchasing and the municipality's measurement of its own green purchasing rate. Regarding the estimation results for the implementation of green purchasing, we find that if a municipality has a GPP, then it tends to implement green purchasing for all items except mobile phones, water heaters, other equipment, and public services. Almost all APEs are larger than 10%. According to column (1) of Table 1, for stationery and office equipment, GPP adoption has the highest APE, which is approximately 19%. The second highest APE, roughly 18%, is found for imaging equipment, electronic devices, and uniforms. The third highest APE, approximately 17%, is found for office furniture and work gloves. After work gloves, the APE declines but remains high. The APE is approximately 15% for lighting equipment. GPP adoption has the same APE, approximately 14%, for paper products, home appliances, and cars. Moreover, the APE is approximately 12% for fire extinguishers. The remaining items have APE values less than 10%. Among the remaining items, the highest APE of approximately 9% is revealed for bedclothes and emergency supplies. The second highest APE is approximately 8% for other fiber products. The lowest APE among the 21 items is approximately 6% for other public services and AC units. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**(1)**} & \multicolumn{2}{c}{**(2)**} \\ \cline{2-5}  & \multicolumn{2}{c}{**Implementation of**} & \multicolumn{2}{c}{**Municipality Measuring Its**} \\  & \multicolumn{2}{c}{**Green Purchasing**} & \multicolumn{2}{c}{**Own Green Purchasing Rate**} \\ \hline  
* APE denotes the average partial effect of \(G\)\(P_{i}\) on corresponding dependent variables for 21 items. Standard errors in parentheses. All the estimations include the natural log of the population, the natural log of the standard financial scale, and prefecture dummies. **\(p<0.05\), *** \(p<0.01\).  
\end{table} 
Table 1: Average partial effects (APEs) of green purchasing implementation and measurement of 21 categories. According to these results and Figure 5 in the previous section, we find that GPP has a higher APE on items for which there is a larger difference in the share of municipalities engaging in green purchasing with and without a GPP. For example, uniforms have higher values in both APE and the difference in green purchasing between municipalities with and those without a GPP. In contrast, several items that have relatively higher values in this difference have lower APEs. For instance, the differences in green purchasing between municipalities with a GPP and those without a GPP for AC units and cars exceed 20%, whereas their APEs are lower than 15%.