Year	PPP $ per kg of oil equivalent
1990	4.89398034095461
1991	5.092667406512266
1992	5.274019395613234
1993	5.335747716848699
1994	5.39947475745847
1995	5.489391884029726
1996	5.733167024366478
1997	5.873453397394358
1998	5.7762206862660745
1999	5.779023214242371
2000	6.053667346219766
2001	6.1863135946976096
2002	6.224878369410642
2003	6.506965475145325
2004	6.785840149497513
2005	7.144378761934145
2006	7.505307857112779
2007	7.901386442590582
2008	8.049465034329424
2009	7.981590825439284
2010	8.300359296550642
2011	8.781221806639216
2012	8.986410459153577
2013	9.271472573960102
2014	9.306347040750888