Fig. 4
From: World trend in energy: an extension to DEA applied to energy and environment
![Fig. 4](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs40008-017-0073-z/MediaObjects/40008_2017_73_Fig4_HTML.gif)
Source: BP Statistical Review of World Energy (2014) (http://www.bp.com/en/global/corporate/about-bp/energy-economics/statistical-review-of-world-energy/statistical-review-downloads.html)
Trend of World Oil Production: Regional Classification. We prepare the figure based upon the numbers listed in the data source. See Sueyoshi and Goto (2017).