Year	constant 2021 PPP $ per kg of oil equivalent
1990	7.016479779533928
1991	7.203066242077667
1992	7.237503053222115
1993	7.483970123763016
1994	7.47272869640293
1995	7.7543176080379235
1996	6.94713190259958
1997	7.079908306302121
1998	7.461607814579869
1999	7.534972087938752
2000	9.23766699298752
2001	9.149443312738898
2002	8.925282197129563
2003	8.75408405263393
2004	8.756451321655877
2005	8.875175293567485
2006	7.8182863255002575
2007	7.621455500881474
2008	7.820911175884154
2009	7.627058598571429
2010	7.330826278455397
2011	7.346159721655233
2012	7.43275196055721
2013	7.622667184582208
2014	7.685402263136834