Year	constant 2011 PPP $ per kg of oil equivalent
1990	8.42436728425075
1991	9.04497002935499
1992	8.48025478244867
1993	8.42251016681605
1994	8.48288212616831
1995	8.622732766961
1996	8.82345024500371
1997	8.69601803483892
1998	8.79685372906241
1999	9.32708824942703
2000	9.23940863091392
2001	8.80595546186385
2002	8.96385644807533
2003	8.62523747586756
2004	9.2322649244912
2005	9.99784050685187
2006	9.57784463742697
2007	9.89767746953443
2008	9.26464161213729
2009	9.96393378233634
2010	9.75052053264742
2011	10.257433570031
2012	9.98938222718886
2013	10.9142319586405
2014	11.5573184931442
2015	11.5571850347774