Year	constant 2011 PPP $ per kg of oil equivalent
1990	8.23918088896818
1991	9.0532671416921
1992	9.58542629277614
1993	7.82766730523979
1994	9.12008791171206
1995	10.5396216060113
1996	11.1171603016791
1997	10.4179339861596
1998	12.4261489729465
1999	11.9333350024161
2000	14.2070076274173
2001	12.2752257386697
2002	13.5598856568309
2003	12.3493667726985
2004	12.3503956523397
2005	12.0673033007924
2006	12.9904950920048
2007	12.8316916388278
2008	13.9038258662391
2009	14.5745247098393
2010	14.0832604127819
2011	14.3465879049811
2012	13.9217115677884
2013	16.6363959166118
2014	17.9145774009429