Year	constant 2011 PPP $ per kg of oil equivalent
1990	9.69547165818971
1991	9.74620056963524
1992	9.72691538053976
1993	10.009217136033
1994	9.94431764570723
1995	9.9516689094524
1996	9.91315821072933
1997	10.0487310800754
1998	9.96485635627157
1999	9.88388096527455
2000	10.1347004723204
2001	10.0555255335995
2002	9.88941591997069
2003	9.82565455340226
2004	9.999479607928
2005	10.0535302450496
2006	10.1352740405406
2007	10.5253541922009
2008	10.5623453798127
2009	10.4262509028441
2010	10.4920131003047
2011	10.76817388749
2012	10.6230688596884
2013	10.7189829782207
2014	10.9296944882801