Year	constant 2021 PPP $ per kg of oil equivalent
1990	13.734724056754448
1991	12.558485156872628
1992	13.381573597901275
1993	13.032516833761575
1994	13.26258884471241
1995	13.791669541368503
1996	12.542079398837549
1997	13.97688154524652
1998	14.522099718678179
1999	15.601638899907043
2000	16.654849256970184
2001	16.291448125751042
2002	16.540702720147767
2003	15.703924952864403
2004	16.665453996198252
2005	17.542140438979803
2006	16.996520679406128
2007	17.572794666775344
2008	17.981417712376324
2009	17.888142413158857
2010	17.203716664802457
2011	18.87031343297883
2012	19.686777841192978
2013	19.574129707022212
2014	21.531920096605702
2015	22.315927613795328