Year	constant 2011 PPP $ per kg of oil equivalent
1995	3.13479434923016
1996	3.00364189267824
1997	3.42397736689718
1998	3.90691803675615
1999	4.12127020679854
2000	4.65315092559322
2001	4.74473005859491
2002	5.25145902732826
2003	5.10512032659774
2004	5.325310061566
2005	5.92949890510503
2006	6.70156581180516
2007	6.45281360776533
2008	6.32553724862732
2009	6.08058510601456
2010	5.38536285373096
2011	5.79156108460191
2012	6.15467490767327
2013	5.68490636187355
2014	5.90363257392598
2015	6.6158833742625