Year	constant 2011 PPP $ per kg of oil equivalent
1990	10.0418820978531
1991	4.53524086631129
1992	4.04726589832399
1993	4.05132412798268
1994	3.71350783310533
1995	3.94777662312271
1996	4.3775767584406
1997	4.46044543987996
1998	8.43147877905244
1999	12.8287504158456
2000	11.0522240172054
2001	10.1138739026353
2002	9.90194147534486
2003	7.20920076677082
2004	10.7989628554884
2005	11.1337841743881
2006	12.9983501993637
2007	12.9502132148231
2008	12.9393028542653
2009	11.1611242734324
2010	10.4296251376355
2011	10.2519897526417
2012	10.4525373021047
2013	10.4509998292161
2014	10.4976457422923