Year	constant 2011 PPP $ per kg of oil equivalent
1990	9.01707249283813
1991	8.76878360656777
1992	8.02043279063614
1993	7.72969478983348
1994	7.60462414272613
1995	8.17720918315219
1996	7.84265618185057
1997	7.97386913738152
1998	8.38830160563491
1999	7.14932152807108
2000	7.24387153654945
2001	7.54128542346972
2002	6.93776141877755
2003	7.23899550434361
2004	5.19989478251192
2005	5.11374519621979
2006	5.27900723484979
2007	4.99125376222986
2008	5.09222120094022
2009	5.73743026002096
2010	5.40054409753212
2011	4.50396678237617
2012	4.59885533366486
2013	4.67562408931239
2014	4.96024429258068