Year	PPP $ per kg of oil equivalent
1990	2.1132234846798497
1991	2.367613144387289
1992	2.572401879677096
1993	2.7389999959970748
1994	2.9604100974417946
1995	3.0777418225679467
1996	3.2946149474836015
1997	3.5397989625453508
1998	3.6054894676978537
1999	3.7775898914475396
2000	3.9881032776066245
2001	4.191680856340719
2002	4.306595646126009
2003	4.264699900453245
2004	4.238664958506682
2005	4.387199400915792
2006	4.62935763777782
2007	4.955460694518114
2008	5.297506039738706
2009	5.392892511977493
2010	5.4524137890112465
2011	5.687343644890736
2012	6.003838166962178
2013	6.205725263012566
2014	6.382319650399559