Year	constant 2021 PPP $ per kg of oil equivalent
1990	4.658926448346788
1991	5.497915869032478
1992	5.4555965008878236
1993	5.012061565233879
1994	5.2630948449583155
1995	4.988853166998144
1996	5.277521004919095
1997	5.00021182161259
1998	5.392780266619704
1999	5.40268097984808
2000	5.562027950485143
2001	5.540988317797619
2002	6.020387735596567
2003	6.182346452431369
2004	6.769887352117879
2005	6.8605083475107165
2006	7.1264027188618435
2007	7.729512059272979
2008	8.314860868953653
2009	9.110753736289869
2010	9.062879050531258
2011	8.59871310970685
2012	9.073200078126806
2013	9.792384130335615
2014	9.34571125692222