Year	PPP $ per kg of oil equivalent
1990	3.4904980240942414
1991	3.5920785140661464
1992	3.6843620187027817
1993	3.852338030097422
1994	3.925907571710422
1995	4.0402822644864615
1996	4.17452040411758
1997	4.379928547441891
1998	4.467629784773255
1999	4.555157295269312
2000	4.844141031773998
2001	4.995856920550909
2002	5.088253519018382
2003	5.272899862269856
2004	5.5876211188126685
2005	5.932611330991078
2006	6.309218616827685
2007	6.679452907617432
2008	6.9704571779609195
2009	7.082451754885153
2010	7.355261791718346
2011	7.552191744087073
2012	7.7432487125417095
2013	8.042325870737324
2014	8.393219348635231