Year	constant 2021 PPP $ per kg of oil equivalent
1990	18.13949329470516
1991	19.044192765688077
1992	19.02465104577427
1993	18.867707258892
1994	18.767502384963237
1995	18.133152095165578
1996	18.841685874689794
1997	18.84620456089873
1998	19.014262441612587
1999	19.641673720155534
2000	19.987466164350767
2001	19.1997556260961
2002	19.47057727156202
2003	19.35363565527791
2004	19.997553369515558
2005	20.517169848784764
2006	20.42695870666795
2007	20.93206702489769
2008	21.14240235910437
2009	21.110295818865584
2010	20.578327771440883
2011	21.11837627247062
2012	21.437413355669236
2013	22.254066579702243
2014	22.602911061648758