Year	constant 2011 PPP $ per kg of oil equivalent
1990	7.27503388110859
1991	7.30459553654955
1992	7.39500478257648
1993	7.38892225490245
1994	7.35133172796379
1995	7.31715085979216
1996	7.51475112514967
1997	7.56497778384423
1998	7.50761294274421
1999	7.40221562040405
2000	7.56681179264634
2001	7.53761210732039
2002	7.4859891884644
2003	7.68251425445103
2004	7.79804143210315
2005	7.97294748166989
2006	8.08422547862028
2007	8.28120548176611
2008	8.22538687028501
2009	8.07851590157092
2010	8.28690978665371
2011	8.53751376307486
2012	8.51015206989941
2013	8.80458024226717
2014	8.91558415451227