Year	PPP $ per kg of oil equivalent
1990	7.196527847096272
1991	7.246583371833992
1992	7.090842241387428
1993	6.8596630135284675
1994	6.690818022203817
1995	6.796601276270317
1996	7.112547881575327
1997	7.1044906781777755
1998	7.423804776526068
1999	7.403888067195601
2000	7.973195768574428
2001	7.685194879031802
2002	7.633026845863313
2003	7.956627743282885
2004	8.256792607861916
2005	8.333087801089595
2006	8.515551181742131
2007	8.761793131996468
2008	8.64684552439865
2009	8.433725762083439
2010	8.570848125109425
2011	8.996006533573619
2012	8.707084754229117
2013	8.766168161191796
2014	8.346079794078832