Year	constant 2011 PPP $ per kg of oil equivalent
1990	10.0579184405041
1991	8.82116196795857
1992	9.57737452865812
1993	9.22111390278621
1994	8.89599038206138
1995	8.93179897455463
1996	8.95017203720594
1997	9.16665266996814
1998	8.99009583777948
1999	9.05971169635021
2000	10.2723023971863
2001	8.16713144912627
2002	8.43441665322362
2003	9.32747951260121
2004	9.57956306902365
2005	9.44753724702518
2006	9.99508600845753
2007	9.50250701497746
2008	8.28848616049338
2009	7.77082873062405
2010	7.6730852656728
2011	7.86740669759857
2012	7.73294942539463
2013	7.94271123066664
2014	8.2303068429621