Year	constant 2011 PPP $ per kg of oil equivalent
1990	6.67965105771144
1991	6.40188215085473
1992	6.51117307047375
1993	6.78447775317417
1994	6.54934914083136
1995	6.54138902284457
1996	6.63699710614662
1997	6.35527358526917
1998	6.13178190137178
1999	6.92297471041407
2000	7.26057903972373
2001	6.91571090453311
2002	6.89638013470914
2003	6.63276197006319
2004	6.53719022755829
2005	6.63284402429031
2006	7.27439961377254
2007	6.57799564138504
2008	6.91281614194564
2009	7.03912781331642
2010	7.13027250965621
2011	6.67779733135017
2012	6.86624036295305
2013	6.95617263811527
2014	6.96096584601148