# Dynamic Evaluation and Internal Driving Factors of Water Resources Green Efficiency in China
## 4 Result and Discussion
### Decomposition of Driving Factors for Water Resources Green Efficiency
#### 4.2.1 Time-Varying Characteristics of Water Resources Green Efficiency Decomposition  
(1) Time-varying characteristics of efficiency decomposition at the national level  
As can be seen from Table 4 and Figure 3, firstly, from the perspective of PEC, the national average for the period 2000-2016 was 1.001, an increase of only 0.1%, indicating a slow rising trend in the PEC. Secondly, from the perspective of SEC, the 2000-2016 national average for the period 2000-2016 was 0.9994, which indicated a decrease of 0.06% compared to the value in 2000. An improvement trend in this index was exhibited only in years 2000-2001, 2001-2002, 2003-2004, 2004-2005, 2007-2008, 2010-2011 and 2015-2016. Moreover, in terms of PTC, the national average for the period 2000-2016 was 1.0122, which indicated an increase of 1.22% compared to the value in 2000, and was higher than the increase in the total factor productivity index (1.07%). It shows that PTC has been improving continuously through the 21 st century. Finally, in terms of STC, the national average for the period 2000-2016 was 1.0007, indicating an increase of 0.7% in this component since 2000. It showed that water resources scale technology has shown a slow upward trend since 2000. From the perspective of national water resources green efficiency decomposition, the increase in PEC indicates that China can effectively use technological innovation to improve the water resources green efficiency, which means that the current technology application has a positive externality. The largest increase in PTC shows that the improvement of China's water resources efficiency mainly depends on technological innovation, which may be due to China's substantial increase in technology research and development expenses in recent years. STC also helps to improve the water resources green efficiency, indicating that technology accumulation in the process of research and development can form a positive scale effect, thereby improving the water resources green efficiency. Where we need to be vigilant is the inhibitory effect of SEC on the water resources green efficiency. The reason for this is that water-saving awareness in water-rich areas is poor, which makes them prone to waste. Generally speaking, while strengthening technology research and development in the future, the country should continue to attach importance to the application of new technologies and tap the potential of existing technologies. This will not only significantly improve the water resources green efficiency, but also help save research and development cost. At the same time, the country urgently needs to strengthen water-saving publicity and policy implementation in areas with abundant water resources to reverse the negative external effects of water resources scale efficiency. (2) Time-varying characteristics of efficiency decomposition at the regional level  
Figure 4 shows that in the eastern region, the PEC of water resources green efficiency greatly improved in 2000-2001 and 2009-2010. SEC decreased much faster in 2006-2007 and 2009-2010 than in other years. PTC showed an upward trend in 2004-2005, but exhibited an abrupt and severe decrease during 2009-2010 that was followed by continuous improvement. STC deteriorated significantly in 2007-2008 and 2010-2011. Figure 3: Changes in components of water resources green efficiency in China during the study period 2000–2016 (PEC = pure technical efficiency change, SEC = scale efficiency change, PTC = pure technology change and STC = scale technology change). The temporal trend of the decomposition of the water resources green efficiency in central China (Figure 5) showed that PEC significantly increased in 2000-2003 and significantly decreased in 2011-2012. SEC significantly deteriorated in 2000---2003 but markedly improved during 2011-2013. PTC deteriorated significantly in both 2000-2004 and 2012-2014. STC showed significant improvement in 2000-2003, but significant deterioration during the period 2013-2015.