Year	constant 2011 PPP $ per kg of oil equivalent
1990	8.61982732257835
1991	8.60405431024132
1992	8.76665157540484
1993	8.47014096141839
1994	9.08815715699569
1995	9.28362588609742
1996	10.0542514455739
1997	10.0031101058462
1998	9.82844635871677
1999	9.57308845867095
2000	9.96297501830579
2001	9.90191141024999
2002	10.8127781894678
2003	10.0583644901775
2004	10.6902596978609
2005	10.8336843167478
2006	10.9455927246428
2007	11.1021573925033
2008	9.56447959313022
2009	9.66951552939938
2010	8.99121778172362
2011	10.9997081599154
2012	10.667440953541
2013	9.80305191516279
2014	11.3336721134108
2015	11.0059111466272