Year	constant 2011 PPP $ per kg of oil equivalent
1990	10.00527657905
1991	9.14842678314476
1992	9.74801855177644
1993	9.49374264348365
1994	9.66134222720845
1995	10.046759417785
1996	9.13647574659411
1997	10.181680026257
1998	10.5788528081852
1999	11.3652601692353
2000	12.132487883828
2001	11.8677625951768
2002	12.0493360370854
2003	11.4397720580738
2004	12.1402130729138
2005	12.7788491550155
2006	12.3813838229638
2007	12.8011797108988
2008	13.0988476208794
2009	13.0308997567204
2010	12.5323190101488
2011	13.746377738945
2012	14.3411441279682
2013	14.2590838140219
2014	15.6852671323581
2015	16.2563896785894