Year	constant 2011 PPP $ per kg of oil equivalent
1990	8.05338163877477
1991	8.5258931745027
1992	8.75067267082133
1993	9.44132273026207
1994	9.39320697312075
1995	8.99632254986664
1996	9.15565256242064
1997	9.59117479841609
1998	9.63105910398487
1999	9.1483107343191
2000	8.96978941357797
2001	9.01369304632976
2002	8.26384728533216
2003	8.40580125169732
2004	8.38945426285278
2005	9.07752075504524
2006	9.01537725045647
2007	9.70176392602966
2008	9.58685496985429
2009	9.27588510925924
2010	9.80571906789449
2011	10.1521168961193
2012	10.0125332253278
2013	9.98349718651246
2014	9.32794205737405