Year	constant 2011 PPP $ per kg of oil equivalent
1990	5.48197436603073
1991	5.63783573300411
1992	7.208911308569
1993	8.06021929677308
1994	8.20852734469308
1995	9.90318959579994
1996	10.1237145281148
1997	10.5673059344372
1998	10.4314541987759
1999	8.77596300959021
2000	9.37575683852925
2001	9.96097276769732
2002	9.4510089260795
2003	10.1945226038924
2004	9.78601058793693
2005	10.3200059239993
2006	11.1960530510802
2007	12.4303471914275
2008	12.8803835356273
2009	13.0071742617659
2010	13.615264413554
2011	13.3440137259366
2012	15.0743086737276
2013	13.0940671041135
2014	13.2357519010098