Year	constant 2021 PPP $ per kg of oil equivalent
1990	11.971753998367642
1991	11.817937856895961
1992	11.485042176072918
1993	10.771993394406682
1994	9.983321439833805
1995	12.280483522083676
1996	11.182815009385562
1997	11.714152147363992
1998	11.613940896311645
1999	12.130282486941926
2000	11.950049978504971
2001	12.555764759931307
2002	12.847515562346253
2003	12.11841619908625
2004	13.587382555650045
2005	14.020835249872869
2006	14.11524399782333
2007	14.044733842760206
2008	13.739082856394765
2009	13.771619407275388
2010	14.563649617216008
2011	15.084406108873964
2012	15.48868208580889
2013	16.68732195500907
2014	16.03997065297278