Year	constant 2011 PPP $ per kg of oil equivalent
1992	3.41063422562249
1993	3.54107571389533
1994	3.8312305054345
1995	3.9768894014902
1996	4.17466476447037
1997	4.42291859870436
1998	4.74286147381533
1999	4.70675541255123
2000	4.73946225835169
2001	4.67273570385146
2002	4.84775702940224
2003	5.13604522995958
2004	5.49039612278618
2005	5.71293394983667
2006	6.25838994220604
2007	7.2429788639728
2008	7.45286455392748
2009	7.71685329994423
2010	7.60827245952834
2011	8.03839718372335
2012	8.51048740567665
2013	8.48972891104535
2014	9.27065274710121
2015	9.45425608264071