Year	constant 2011 PPP $ per kg of oil equivalent
1990	9.67309419511159
1991	9.39878909954839
1992	9.98640670187743
1993	9.92540164929624
1994	10.1914277643268
1995	10.0165300434438
1996	9.64665538967144
1997	9.92063373122646
1998	10.1046981596604
1999	10.4867510295033
2000	10.8792655041093
2001	10.4261751743429
2002	10.5038911190154
2003	10.0202663486211
2004	10.1440053880982
2005	10.1045640461845
2006	10.4192115193171
2007	10.9313197193726
2008	11.0218632433354
2009	11.2309521844134
2010	10.6971367558721
2011	11.334487598645
2012	11.4623822790124
2013	11.3040576465487
2014	11.7573845306018
2015	11.644807251316