## 3 Results
### Results of Regression Analysis
#### 3.2.2 Results of Subsamples on Subject Matters  
It is widely accepted that different types of procurement subject matters possess different features. When looking into each branch of product, service, and work, the influential factors may be diverse. In Table 6, we separate our sample into three subgroups according to the subject matters of the contracts, and only show the significant coefficients. For product contracts, a framework agreement, the number of SMEs, and being related to the medical products sector reduce the possibility of a contract being green. In contrast, the contract value, GPA, joint procurement, business service sector, transport equipment sector, and food sector increase this possibility. In service procurements, OPE, a framework agreement, the number of offers, being funded by the EU, the health sector, business service sector, and construction work sector are significantly and negatively related with a green contract. The two factors that are positively related are the contract value and number of SMEs. The sample size of work contracts is the smallest one, and we obtain significant negative significant coefficients for a framework agreement and the number of SMEs. In contrast, we obtain positive ones for contract value and the number of awards. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Regressors**} & \multirow{2}{*}{\begin{tabular}{c} **(1)** \\ **Product** \\ \end{tabular} } & \begin{tabular}{c} **(2)** \\ **Marginal** \\ **Effect** \\ \end{tabular} & \begin{tabular}{c} **(3)** \\ **Service** \\ \end{tabular} & \begin{tabular}{c} **(4)** \\ **Marginal** \\ **Effect** \\ \end{tabular} & \
\begin{tabular}{c} **(5)** \\ **Work** \\ \end{tabular} &
\begin{tabular}{c} **(6)** \\ **Marginal** \\ **Effect** \\ \end{tabular} \\ \hline \hline \multicolumn{6}{c}{**Contracts and procedures**} \\ \hline OPE & & & \(-0.33\)*** & \(-0.076\)*** & & \\  & & (0.043) & (0.010) & & \\ \hline Contract value & \(0.014\)* & \(0.0025\)* & \(0.022\)*** & \(0.0052\)*** & \(0.035\)* & \(0.0079\)* \\  & \((0.0072)\) & \((0.0013)\) & \((0.0049)\) & \((0.0012)\) & \((0.021)\) & \((0.0048)\) \\ \hline Framework agreement & \(-0.13\)** & \(-0.025\)** & \(-0.099\)** & \(-0.023\)** & \(-0.026\)* & \(-0.059\)* \\  & \((0.060)\) & \((0.011)\) & \((0.048)\) & \((0.011)\) & \((0.15)\) & \((0.034)\) \\ \hline GPA & \(0.18\)*** & \(0.032\)*** & & & & \\  & \((0.057)\) & \((0.010)\) & & & & \\ \hline Funded by EU & & & \(-0.23\)*** & \(-0.054\)*** & & & \\  & & & \((0.064)\) & \((0.015)\) & & & \\ \hline Electrical auction & & & & & & \\ \hline Award criteria & & & & & & \\ \hline \hline \multicolumn{6}{c}{**Purchasers**} \\ \hline CPB & & & & & & \\ \hline Joint procurement & \(0.22\)** & \(0.040\)** & & & & \\  & \((0.10)\) & \((0.019)\) & & & & \\ \hline \hline \multicolumn{6}{c}{**Tenderers**} \\ \hline SMEs & & & & & & \\ \hline Number of SMEs & \(-0.020\)** & \(-0.0036\)** & \(0.029\)*** & \(0.0068\)*** & \(-0.060\)** & \(-0.014\)** \\  & \((0.0088)\) & \((0.0016)\) & \((0.01)\) & \((0.0023)\) & \((0.026)\) & \((0.0059)\) \\ \hline Awarded to a group & & & & & \\ \hline Number of offers & & & \(-0.032\)*** & \(-0.0076\)*** & & \\  & & & \((0.0091)\) & \((0.0021)\) & & \\ \hline Number of awards & & & & & \(0.030\)*** & \(0.0068\)*** \\  & & & & & \((0.0099)\) & \((0.0022)\) \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Regression results with subsamples of subject matters. The dependent variable is “green contract”. Compared with the results of integrated regression in Table 5, the coefficients of contract value in three subsamples are also positive, within a 10% significance level. That increases the credibility of the positive relation between the contract value and green features of a contract. However, the coefficient in a service group is more significant (within 1%). Analysis for framework agreements is similar; the results in the total sample and the three subsamples are all negative, and those for the product group and service group are more significant (within 5%).