Year	constant 2011 PPP $ per kg of oil equivalent
1990	11.950613362189
1991	11.8070112360587
1992	10.7766385694082
1993	10.2393897086505
1994	9.78564031319085
1995	9.75096180760092
1996	9.34961728718636
1997	9.91243261771053
1998	9.57056710491562
1999	9.04708699956124
2000	9.13935762728806
2001	8.79569281708885
2002	7.71778692681888
2003	8.48454444185539
2004	8.60710162957844
2005	8.88323556921566
2006	8.2402019791859
2007	8.12173248595854
2008	7.73525123784835
2009	7.11666186928746
2010	6.71580157447887
2011	7.69268593475249
2012	7.20937486697867
2013	7.71863902086505
2014	7.20149662902552