Year	constant 2011 PPP $ per kg of oil equivalent
1990	6.8454787494869
1991	6.74369974770548
1992	7.12319787640908
1993	7.52394324715722
1994	7.36783680587432
1995	7.34326892601233
1996	7.30650529798348
1997	7.38858387501645
1998	7.35906648721381
1999	7.63375237075981
2000	7.60153024722827
2001	8.0825693450332
2002	8.14005088361033
2003	8.29281310507913
2004	7.49053745496422
2005	7.54470937324486
2006	7.9444287406584
2007	8.1703069144862
2008	8.93472409658621
2009	8.93248625904591
2010	9.59532198056613
2011	9.89556739147767
2012	9.14349300797514
2013	9.55111109268963
2014	9.30245299629604