Year	constant 2011 PPP $ per kg of oil equivalent
1990	2.03815001881369
1991	2.07148809346047
1992	2.43150254457719
1993	2.64462501621197
1994	2.92735652447083
1995	3.24478220903904
1996	3.00455864998872
1997	3.51124030375783
1998	3.36808232516872
1999	3.99532272562202
2000	4.38233237761952
2001	4.96532890224592
2002	4.41823914031366
2003	4.44188600144079
2004	4.82308957620974
2005	4.75418780421036
2006	4.98039828918759
2007	4.63632103190387
2008	4.69896719763298
2009	5.29477800100936
2010	5.52069283549777
2011	4.8653590020602
2012	3.88839321347945
2013	4.51475313753007
2014	4.88452558176732