Year	constant 2011 PPP $ per kg of oil equivalent
1990	4.06875691540894
1991	3.72162257931763
1992	3.27103807149565
1993	2.77492450269836
1994	2.65710763688582
1995	2.56687256437905
1996	2.45710358215463
1997	2.27902735282769
1998	2.18843214281999
1999	2.08643424785075
2000	1.94026301029034
2001	1.83780470576413
2002	1.82844873435633
2003	1.8610323499989
2004	1.91027981841743
2005	1.95197098084571
2006	1.98081041116674
2007	2.03088395938075
2008	2.08051177860167
2009	2.0775661965983
2010	2.14623636660884
2011	2.15984660564007
2012	1.86417362673699
2013	1.92428127042239
2014	2.01594734318348