Year	constant 2011 PPP $ per kg of oil equivalent
1990	10.5835286081747
1991	9.95350027896221
1992	9.57337978992716
1993	9.19482593225471
1994	8.94716890314816
1995	8.99654482435452
1996	9.06975364447462
1997	9.16232533985536
1998	9.622485944397
1999	9.63734091557773
2000	9.7669827224773
2001	9.24069161466893
2002	8.86066656598783
2003	9.10838454778148
2004	9.35855329376905
2005	9.35999760012653
2006	9.27693361080091
2007	9.28756060212409
2008	9.13206899220264
2009	8.71061165180259
2010	8.59978940423659
2011	8.79819241490846
2012	8.58678538724783
2013	8.82301669720147
2014	8.5946644358504