Year	constant 2011 PPP $ per kg of oil equivalent
1990	10.2519811050497
1991	10.1353582794741
1992	10.0427630858166
1993	10.3627226998001
1994	10.0520109460891
1995	9.87407017460629
1996	10.289629040564
1997	10.0386720853092
1998	9.96775215957794
1999	9.9338023948338
2000	9.97653433237536
2001	10.1116525104179
2002	10.101871338903
2003	10.0770133659536
2004	9.96184039309102
2005	10.1193383611617
2006	10.5510315850932
2007	10.7953730272468
2008	11.2888718258276
2009	11.8405243041614
2010	11.8514580881562
2011	11.9226893965325
2012	11.5933365161654
2013	12.2124298430073
2014	12.6571786983255
2015	12.583890865069