Year	constant 2011 PPP $ per kg of oil equivalent
1999	7.50764251413242
2000	7.41780014556445
2001	7.07272701894607
2002	6.73558532563832
2003	7.39861808255336
2004	7.51801989087933
2005	8.48858157982907
2006	8.94166585046447
2007	10.2273870410631
2008	9.85705933001242
2009	9.01893638934584
2010	8.7948749443967
2011	5.0648639583698
2012	8.96824734259383
2013	6.88378896702235
2014	5.68440416979763