Year	constant 2021 PPP $ per kg of oil equivalent
1990	2.8284085021658294
1991	2.369357543650633
1992	2.712427073566052
1993	4.660359325011078
1994	7.8123659682423785
1995	7.000333938308885
1996	6.843243525001314
1997	6.76371634607917
1998	7.125620634262474
1999	7.6129884853680325
2000	7.337265201708875
2001	8.077145053279702
2002	9.773715541752027
2003	10.552438574874984
2004	11.02843584038765
2005	10.473648614797199
2006	11.64170551864521
2007	11.871331805030966
2008	12.051624005697633
2009	11.915523455947564
2010	12.799342561065894
2011	12.254216148580369
2012	12.008751303068875
2013	12.705427108592795
2014	12.90311074555427