Year	constant 2021 PPP $ per kg of oil equivalent
1990	1.5513732543392849
1991	1.5624178130315987
1992	2.0755582653892204
1993	2.4369618834204405
1994	6.994819336825853
1995	7.790784952014509
1996	10.28526998255803
1997	9.103087503295015
1998	8.541257111160437
1999	9.453138024296381
2000	7.597949284604208
2001	8.052775592713626
2002	8.061986591836757
2003	8.387528925695024
2004	8.157485572953085
2005	8.087244198463807
2006	8.106770202751475
2007	8.575055955625198
2008	8.04470975264505
2009	7.48181182862984
2010	7.239355783520174
2011	6.6294165719645
2012	7.028925825169412
2013	7.450495631788509
2014	6.21680908384842