Year	constant 2011 PPP $ per kg of oil equivalent
1990	8.97152952713046
1991	8.96869638872479
1992	9.09841048929043
1993	9.33394996366237
1994	9.11598242988777
1995	9.01256906103259
1996	8.51571005504848
1997	8.12972380169599
1998	8.0086838187675
1999	7.84459050253008
2000	8.00335273529537
2001	8.04497521803908
2002	7.72241244479463
2003	7.6412298616707
2004	7.51588471613639
2005	7.61628065787148
2006	7.8401774928268
2007	7.93022668192927
2008	7.85312753298422
2009	7.82786140255852
2010	7.69191321448542
2011	7.76570274500234
2012	7.76749830331704
2013	7.41675177894347
2014	7.54313009476241