Year	constant 2011 PPP $ per kg of oil equivalent
1990	7.94541412665578
1991	8.03113440881516
1992	8.39952114451635
1993	8.46526650421777
1994	8.52956414275263
1995	9.27105527272425
1996	9.34068067496207
1997	9.8362961881255
1998	10.0785207104786
1999	10.6182582014925
2000	11.2069332697881
2001	11.3408026845994
2002	11.9798009041679
2003	12.6472912375319
2004	13.0926979642547
2005	13.7511531511553
2006	14.3905914865308
2007	14.759925759562
2008	14.3263698704061
2009	14.0781085921686
2010	14.2440060237757
2011	15.654261230611
2012	15.6906604979797
2013	16.033232599555
2014	17.7410203853885
2015	21.3855119951381