Year	constant 2021 PPP $ per kg of oil equivalent
1990	9.868652962036482
1991	9.973019414307027
1992	10.304301150976546
1993	10.273616100148201
1994	10.609184761368457
1995	10.53938012864173
1996	10.40316472802121
1997	10.7444926541752
1998	11.006807932806582
1999	11.433511509350708
2000	11.79952772706408
2001	11.752714528111106
2002	11.881971360357854
2003	11.754898039530115
2004	11.931652366415788
2005	12.142726817760483
2006	12.501977092534277
2007	13.105807752292932
2008	13.258663574125965
2009	13.472187431980393
2010	13.22490296595133
2011	13.955656460039702
2012	14.038832946464582
2013	14.187976361769584
2014	14.93796878453086
2015	15.062124104928914