Year	constant 2021 PPP $ per kg of oil equivalent
1990	10.974316134678046
1991	11.035395823809539
1992	11.373381730528255
1993	11.35164947777497
1994	11.648978805106756
1995	11.535658647453959
1996	11.360358157369337
1997	11.68314559338532
1998	11.83178820416945
1999	12.185407646247159
2000	12.495907954829669
2001	12.442573066276148
2002	12.559442859045499
2003	12.392161178637283
2004	12.499544462935043
2005	12.683713736537895
2006	13.065263841508633
2007	13.681462747410219
2008	13.77331024539983
2009	13.914211865164424
2010	13.725339053591288
2011	14.53772288956441
2012	14.545997219775304
2013	14.632550432166553
2014	15.411758115964073
2015	15.485856650685614