Year	constant 2011 PPP $ per kg of oil equivalent
1990	5.2005211760387
1991	5.17810582805961
1992	5.00500791576983
1993	4.90045701573143
1994	4.97469234959624
1995	4.95701050148416
1996	4.9806012397008
1997	4.94534337360731
1998	4.92404644916894
1999	4.92940104478561
2000	4.78986043397379
2001	4.90414818590975
2002	4.86621296749326
2003	4.90150427969277
2004	4.90016787529447
2005	5.00984737886186
2006	5.11596464286414
2007	5.34977731436039
2008	5.17969139526252
2009	5.05302273118931
2010	5.24496763984939
2011	5.45203422144793
2012	5.63193805588781
2013	5.63783465253145
2014	5.36228104537896