Year	constant 2011 PPP $ per kg of oil equivalent
1990	9.79998559382649
1991	9.81415098298953
1992	9.84286038654554
1993	10.9033435327658
1994	9.73938664075306
1995	9.80033992245444
1996	9.95085715683447
1997	9.70985868266387
1998	9.80459040334406
1999	9.98621674766481
2000	9.72573601910679
2001	10.2748989782184
2002	10.1176510207941
2003	10.5459590791526
2004	11.9599974061936
2005	12.0386764852719
2006	12.6948710350389
2007	13.4076037821845
2008	13.7993512806826
2009	14.1946507000165
2010	14.6332660401415
2011	14.8189496415101
2012	14.4155093857396
2013	16.0372430571051
2014	17.242519195738