Year	PPP $ per kg of oil equivalent
1990	4.805896904705108
1991	4.542023471138287
1992	4.480049835389734
1993	4.08125662631753
1994	4.501419263786195
1995	4.756344406942469
1996	4.970146867771382
1997	5.065225782188237
1998	5.082158538279136
1999	5.14928206474131
2000	5.684860182337483
2001	5.755416336589651
2002	6.256065478175519
2003	6.135452454612717
2004	6.586818860013255
2005	6.834000316814549
2006	7.845132213178557
2007	8.37206687980153
2008	9.225100034688747
2009	9.18609351796731
2010	9.194102435988803
2011	9.881339056962638
2012	10.654408027279745
2013	11.199409534245014
2014	11.836179327000112