## 5 Experimental Results  
### Results of Eco-Efficiency of DMUs  
Table 6 shows the eco-efficiency scores obtained from the SBM DEA for the 17 DMUs from 2013 to 2017.  
The higher the score, the higher the eco-efficiency. An eco-efficiency score of 1 means a best use of inputs to maximize the desirable output (GDP) and minimize the undesirable output (CO\({}_{2}\)).  
From the last column in the Table 5, the overall average eco-efficiency score is 0.835 for all 17 countries in the time period 2013-2017. There are nine countries with the best eco-efficiency score of 1--France, Hungary, Greece, Italy, the The Netherlands, Poland, Portugal, Switzerland, and the United Kingdom. The other eight countries--Austria, Belgium, the Czech Republic, Finland, Germany, Norway, Spain, and Sweden--have recessive eco-efficiency scores ranging between 0.559 and 0.704. Finland recessed the most (0.559). These countries performed stably as their scores change slightly. However, a likely downward trend is found based on the average eco-efficiencies (0.872, 0.860, 0.814, 0.809, 0.822) from 2013 to 2017, respectively.  
As the results show that eight of the 17 countries are relatively inefficient, more effort is required for the eight countries to improve this efficiency. However, as these eco-efficiency scores are relative values (instead of absolute values), this implies that the nine countries with the best eco-efficiency score of 1 may still have room for improvement. Section 5.2 provides a change analysis to better understand the inefficiency sources for these countries.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**DMU** & **2013** & **2014** & **2015** & **2016** & **2017** & **Average** \\ \hline Austria & 0.644 & 0.643 & 0.604 & 0.593 & 0.603 & 0.617 \\ Belgium & 0.671 & 0.640 & 0.613 & 0.603 & 0.663 & 0.638 \\ Czech Republic & 0.709 & 0.669 & 0.617 & 0.607 & 0.662 & 0.653 \\ Finland & 0.582 & 0.581 & 0.547 & 0.539 & 0.548 & 0.559 \\ France & 1 & 1 & 1 & 1 & 1 & 1 \\ Germany & 0.7181 & 0.7022 & 0.6729 & 0.6685 & 0.7016 & 0.693 \\ Greece & 1 & 1 & 1 & 1 & 1 & 1 \\ Hungary & 1 & 1 & 1 & 1 & 1 & 1 \\ Italy & 1 & 1 & 1 & 1 & 1 & 1 \\ Netherlands & 1 & 1 & 1 & 1 & 1 & 1 \\ Norway & 1 & 1 & 0.509 & 0.504 & 0.507 & 0.704 \\ Poland & 1 & 1 & 1 & 1 & 1 & 1 \\ Portugal & 1 & 1 & 1 & 1 & 1 & 1 \\ Spain & 0.783 & 0.713 & 0.655 & 0.625 & 0.659 & 0.687 \\ Sweden & 0.724 & 0.675 & 0.623 & 0.611 & 0.622 & 0.651 \\ Switzerland & 1 & 1 & 1 & 1 & 1 & 1 \\ United Kingdom & 1 & 1 & 1 & 1 & 1 & 1 \\
**Average** & 0.872 & 0.860 & 0.814 & 0.809 & 0.822 & 0.835 \\ \hline \end{tabular}
\end{table}
Table 6: Results of eco-efficiency obtained from Slacks-based measure (SBM) DEA for the 17 DMUs (2013 to 2017).  
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & **X1** & **X2** & **X3** & **X4** & **Y1** & **Y2** \\ \hline X1 & 1 & 0.7636044 & 0.6306863 & 0.6709415 & 0.6777861 & 0.28292 \\ X2 & 0.7636044 & 1 & 0.4443673 & 0.5048966 & 0.8775034 & 0.0364256 \\ X3 & 0.6306863 & 0.4443673 & 1 & 0.4940977 & 0.5254103 & \(-\)0.3450647 \\ X4 & 0.6709415 & 0.5048966 & 0.4940977 & 1 & 0.5153736 & 0.0585877 \\ Y1 & 0.6777861 & 0.8775034 & 0.5254103 & 0.5153736 & 1 & \(-\)0.0716156 \\ Y2 & 0.28292 & 0.0364256 & \(-\)0.3450647 & 0.0585877 & \(-\)0.0716156 & 1 \\ \hline \end{tabular}
\end{table}
Table 5: Pearson correlation coefficients obtained for the year 2017.