Year	constant 2011 PPP $ per kg of oil equivalent
1990	3.28266462458599
1991	2.67739950640458
1992	2.77566543585122
1993	2.87366404655345
1994	3.39402087243574
1995	3.61903422177516
1996	4.39263737258886
1997	4.65942837509464
1998	4.77691850246094
1999	4.91689776948797
2000	4.65666972010227
2001	4.75811929408973
2002	4.65397285834316
2003	5.09875551497511
2004	5.47764442249373
2005	5.10017721785698
2006	4.8663376054951
2007	5.12141392131443
2008	5.55611889015013
2009	5.28029903229627
2010	5.30404579077297
2011	5.68594996736726
2012	5.77204216221378
2013	5.84811879753255
2014	6.17365016741234