Year	constant 2021 PPP $ per kg of oil equivalent
1990	5.645438644070379
1991	5.503299791422399
1992	5.659500738949742
1993	5.708471950100581
1994	6.169753906208048
1995	6.252176773841687
1996	6.337173284581608
1997	6.587642010954884
1998	7.092969887942879
1999	7.600836595192779
2000	8.005401801879632
2001	8.044951791593752
2002	8.304359871142301
2003	8.372523102707062
2004	8.873729626764401
2005	9.205510384704459
2006	9.571762873356183
2007	10.201979090310727
2008	10.634279424857104
2009	11.019550119016952
2010	10.731995422359848
2011	11.131668277827972
2012	11.571387168568192
2013	11.924352122356071
2014	12.54324855196571