Year	constant 2021 PPP $ per kg of oil equivalent
1990	6.612858276079204
1991	6.800872495366351
1992	8.69604737748926
1993	9.72297284173155
1994	9.901875558068067
1995	11.946131978271387
1996	12.212149296483322
1997	12.747249775234652
1998	12.583296232582997
1999	10.586388754795369
2000	11.309512347953376
2001	12.01578920214709
2002	11.400251824540218
2003	12.296948330524316
2004	11.804710887778368
2005	12.448449310538958
2006	13.505504641453237
2007	14.99486494345047
2008	15.537759137951186
2009	15.691360431622995
2010	16.424946369894634
2011	16.09771979121666
2012	18.185032214813802
2013	15.796154044827857
2014	15.967774815677807