Year	constant 2021 PPP $ per kg of oil equivalent
1990	11.812950284154585
1991	10.799139792873289
1992	10.414460551418808
1993	9.267738188787401
1994	10.008151733507843
1995	10.357765022003411
1996	10.641290774510939
1997	10.68263241212682
1998	10.572583880704334
1999	10.609655120634041
2000	11.346429103403429
2001	11.272168027732052
2002	11.594521624167626
2003	11.412961006904597
2004	11.895172509202592
2005	12.224030532177677
2006	12.916445024310683
2007	13.052072028946078
2008	13.658206908574112
2009	13.105473892398189
2010	13.102910265825589
2011	13.416900407755408
2012	13.927434908835064
2013	14.18229112121652
2014	14.834811345425274