Year	PPP $ per kg of oil equivalent
1990	3.848370331674517
1991	3.927606702909106
1992	4.061200248684526
1993	4.166018506603363
1994	4.354380515041919
1995	4.500383726369231
1996	4.7085766216767695
1997	4.805814612362753
1998	4.934503801387685
1999	5.075600480851574
2000	5.314055122899765
2001	5.553324036439402
2002	5.705478307219994
2003	6.020872748452264
2004	6.323314583171336
2005	6.717236496650023
2006	7.137508782945179
2007	7.5050217283341265
2008	7.681964245589292
2009	7.7848530601510735
2010	8.083280446936747
2011	8.302282586543587
2012	8.688584044670053
2013	9.093806327506794
2014	9.298449886112298