Year	constant 2011 PPP $ per kg of oil equivalent
1990	9.59384468600521
1991	9.65349463820527
1992	9.63419760040427
1993	9.92678067889603
1994	9.86822474535558
1995	9.8790590425864
1996	9.81045246690545
1997	9.93932857453866
1998	9.84777602410859
1999	9.72298928952159
2000	9.94064431276825
2001	9.86861292351996
2002	9.7063520665025
2003	9.65098557882698
2004	9.82239453362682
2005	9.86444314570497
2006	9.93833649119899
2007	10.2993246937915
2008	10.359955827558
2009	10.2312585442247
2010	10.3019844893991
2011	10.550835359295
2012	10.4197184014838
2013	10.5205364791009
2014	10.7439505567994