Year	constant 2011 PPP $ per kg of oil equivalent
1990	4.64277121404525
1991	4.6816496641887
1992	4.80093358681883
1993	4.91294747404582
1994	5.09420711942465
1995	5.1308565028835
1996	5.29949537809837
1997	5.51130298377142
1998	5.63548069572567
1999	5.73401899037991
2000	5.92719598599013
2001	5.99737832112574
2002	6.05493853313576
2003	6.00347532529043
2004	6.03163764251456
2005	6.11704791841045
2006	6.25336477460512
2007	6.47631067663217
2008	6.61273960144389
2009	6.61931521006643
2010	6.62657162781993
2011	6.71603956198444
2012	6.82651227470577
2013	7.02786783320683
2014	7.22083933513759