有很多种不同的指标，恐怕不存在公认的“用得最多”或“最好”的单一指标
可参考以下这篇文章，里面的Table 3对几种比较常见的指标有介绍

https://www.sciencedirect.com/science/article/pii/S0959652616312616

Shenggang Ren, Xiaolei Li, Baolong Yuan, Dayuan Li, Xiaohong Chen,
The effects of three types of environmental regulation on eco-efficiency: A cross-region analysis in China,
Journal of Cleaner Production,
Volume 173,
2018,
Pages 245-255,