Year	constant 2021 PPP $ per kg of oil equivalent
1990	10.612361430297664
1991	11.188465898852726
1992	11.50179267513675
1993	11.962185442534059
1994	11.685587813071312
1995	11.846407756245105
1996	11.42279213076848
1997	10.955166546404325
1998	11.02229931336957
1999	10.345595943597502
2000	10.799587769648129
2001	11.3523759171201
2002	11.317232082025267
2003	11.729832246677866
2004	11.74946965057746
2005	12.06156863897848
2006	12.288888995164006
2007	12.460272750365762
2008	13.057511333771485
2009	13.26418040899023
2010	13.437265925291278
2011	13.100618198474072
2012	12.56233345256779
2013	12.479114684027433
2014	13.614706927476599
2015	13.932521056501734