Year	constant 2011 PPP $ per kg of oil equivalent
1990	17.8563056404628
1991	18.1948073226636
1992	16.2686913769728
1993	17.4273860614557
1994	18.3028468352802
1995	18.8140467586856
1996	19.9024240383903
1997	21.7472534649514
1998	15.6773245551406
1999	13.1072304018749
2000	16.6826288981944
2001	16.0955149396586
2002	17.6312677193368
2003	17.6619446066291
2004	20.4405919682737
2005	22.1866209451637
2006	22.5155559712806
2007	22.3149271231406
2008	23.2443624601868
2009	21.5389489707156
2010	24.7131266476967
2011	23.9965884645955
2012	25.2558925702903
2013	26.613453853563
2014	26.7900722862054