Year	constant 2011 PPP $ per kg of oil equivalent
1990	1.36699455137437
1991	1.22734684334067
1992	1.09423932319341
1993	1.18834528257561
1994	1.18043537143864
1995	1.20803831547564
1996	1.31340433856651
1997	1.31685487972421
1998	1.23351660091485
1999	1.26179410704549
2000	1.29815793885492
2001	1.35493878220425
2002	1.33579871543461
2003	1.26663494748041
2004	1.39677205772117
2005	1.52417573724549
2006	1.63968184856039
2007	1.77196024808486
2008	1.90548243789915
2009	2.01695871412184
2010	2.2079639195287
2011	2.3745691709617
2012	2.50784515380388
2013	2.67976326380546
2014	2.86732109093822