Year	constant 2011 PPP $ per kg of oil equivalent
1990	8.01010813061839
1991	9.67190408550478
1992	11.1136027287968
1993	8.59363113995414
1994	8.47910880713004
1995	7.87311951958647
1996	8.30876428955582
1997	7.43527377797729
1998	7.84416752889204
1999	7.45793847320724
2000	8.31437282510563
2001	8.0534716826473
2002	8.38269582610927
2003	8.64404032264774
2004	9.09335624985842
2005	9.79676434944415
2006	10.4789142307564
2007	13.0010880301156
2008	11.0504339378284
2009	9.93405170022182
2010	11.1867099540977
2011	11.3462900344032
2012	10.3146530663661
2013	10.734040618266
2014	10.3200551464478