Year	constant 2011 PPP $ per kg of oil equivalent
1992	3.94917181108581
1993	4.26775986552484
1994	5.01541266304025
1995	4.91255644286832
1996	5.11331097888763
1997	5.5527479214353
1998	8.69279749219202
1999	8.38490498154856
2000	8.04786627769819
2001	8.35322202105228
2002	8.52727999549653
2003	7.75130311347072
2004	8.47631716463612
2005	8.48471423579338
2006	9.22319486549297
2007	9.05794491354913
2008	8.68619874936041
2009	8.43098182667863
2010	8.3949924825417
2011	8.89785251703151