Year	constant 2011 PPP $ per kg of oil equivalent
1990	9.22926821266397
1991	8.68699585149273
1992	8.16392906148238
1993	7.41930005833376
1994	6.78521872123265
1995	8.52578531937495
1996	8.77725949577404
1997	8.46842966412367
1998	9.16361667593674
1999	10.6496621288762
2000	11.2965990928335
2001	9.7978117851096
2002	10.2479905210304
2003	8.85949190095799
2004	8.10416112894992
2005	12.3891159253069
2006	12.5704875719199
2007	14.7957314689255
2008	13.1213917089648
2009	15.2508716014006
2010	14.592865072521
2011	14.9993602799506
2012	15.8202129789172
2013	16.3755353983582
2014	16.0032199565691