Year	constant 2011 PPP $ per kg of oil equivalent
1990	9.34450845018309
1991	9.80421975424671
1992	9.50474648643616
1993	9.97891711756253
1994	9.52646345219297
1995	9.62739204345503
1996	9.86863983267151
1997	10.0886811213836
1998	9.69903826164914
1999	9.95141467030537
2000	10.0550145699891
2001	9.88827666594282
2002	9.88760916621895
2003	10.0766541088533
2004	10.1545689437597
2005	10.6960582841366
2006	10.6944996262293
2007	11.0496131731403
2008	11.0436623010338
2009	11.7141428115777
2010	10.799952836085
2011	11.0983621893459
2012	11.0568025170183
2013	11.1906120122919
2014	11.4104995388427