Year	constant 2021 PPP $ per kg of oil equivalent
1990	13.635058826242542
1991	13.757953548033981
1992	13.994863101834131
1993	14.099186270342843
1994	14.410251115851214
1995	14.899423209917241
1996	14.843750602135207
1997	15.823277368368075
1998	15.195703828423774
1999	16.277506123986885
2000	16.673684314615944
2001	17.023432895560774
2002	17.798206049364342
2003	18.114927013337656
2004	18.88645096319923
2005	19.00530184364841
2006	19.297075382929524
2007	20.72590187341946
2008	20.44639748360988
2009	19.94813418355983
2010	20.51111809112043
2011	21.901850106822742
2012	22.547137327126432
2013	22.219155980061124
2014	22.977250711468383