Year	PPP $ per kg of oil equivalent
1990	4.037466315863594
1991	4.1772335466804185
1992	4.327259742599624
1993	4.417250319492037
1994	4.573996487783082
1995	4.69562006908837
1996	4.797915246521818
1997	5.006933789899295
1998	5.161596305262815
1999	5.310706459954893
2000	5.555480644226138
2001	5.786594219295341
2002	5.9693051242435615
2003	6.110833663771976
2004	6.3611900637574585
2005	6.6667469510352495
2006	7.153335403000491
2007	7.52293227740182
2008	7.875294543843692
2009	8.061191300422358
2010	8.152139642944745
2011	8.696774039210833
2012	9.048957064721405
2013	9.389302597112344
2014	9.794261644247975
2015	10.084943339702528