Year	PPP $ per kg of oil equivalent
1990	1.279680807719492
1991	1.4842428728906556
1992	1.6769772262692875
1993	1.845668884578849
1994	2.03451436088526
1995	2.146531521210369
1996	2.337701995144105
1997	2.6004082667634214
1998	2.816617817113862
1999	3.0170068298884374
2000	3.2454319564495933
2001	3.4545072571939723
2002	3.586796534190699
2003	3.5219125134929987
2004	3.491477212338271
2005	3.6284846137192317
2006	3.8565566289915947
2007	4.183635168956882
2008	4.533044545595802
2009	4.670312954102044
2010	4.7352519941227635
2011	4.936465537000112
2012	5.22606966029663
2013	5.449344267383046
2014	5.709720164795058