Year	constant 2011 PPP $ per kg of oil equivalent
1990	2.77672680064367
1991	2.78305998202775
1992	2.65825912460201
1993	2.28116126546782
1994	2.01835160483867
1995	1.89455981443002
1996	2.27078255145237
1997	2.4936790155174
1998	2.64242777472702
1999	3.05160572729881
2000	3.28036250215701
2001	3.55819833106467
2002	3.85537070647607
2003	4.03962833759553
2004	4.19693906518162
2005	5.11407057466663
2006	6.97772041244495
2007	9.56338645711874
2008	9.61565584553848
2009	11.7376700251278
2010	12.6730603121402
2011	11.5048313944952
2012	10.7873603214404
2013	11.2624432206043
2014	11.2201673811325