Year	constant 2011 PPP $ per kg of oil equivalent
1990	9.73640679923238
1991	9.94227804445364
1992	9.54125408859765
1993	9.30552056152847
1994	8.8483281048278
1995	8.25354508381432
1996	8.01160991117395
1997	7.70979387793426
1998	8.01093975253126
1999	8.18662442984253
2000	7.50157049646269
2001	9.80362704296747
2002	8.38094456266292
2003	8.27984833196455
2004	8.61488107798517
2005	8.24797670487559
2006	6.90611461543827
2007	8.86337555342575
2008	8.84619713579585
2009	8.77758672859227
2010	8.39019690255657
2011	8.35823165062885
2012	7.64241264462288
2013	8.11785629797132
2014	8.01824573281731