Year	constant 2011 PPP $ per kg of oil equivalent
1990	1.74902806970074
1991	1.92284715866568
1992	2.39372442624728
1993	2.40359890988881
1994	1.56804345101944
1995	1.4140199373158
1996	1.72700353268631
1997	1.52816364024449
1998	1.56487906310148
1999	1.53975153414035
2000	1.61865274399363
2001	1.65753230663927
2002	1.59269591583305
2003	1.47520163569369
2004	1.4836175027723
2005	1.61048053222082
2006	1.74502948494355
2007	1.7007882151095
2008	1.92800382788144
2009	2.32952474104443
2010	2.22961974802136
2011	2.35071977155734
2012	2.52389494337294
2013	2.71050614401396
2014	2.92886530777434