Year	constant 2011 PPP $ per kg of oil equivalent
1990	2.82638445697834
1991	2.85557665179068
1992	3.03721176939656
1993	3.24668132084334
1994	3.28264249425068
1995	3.3942906526924
1996	3.60609507919013
1997	3.731490821071
1998	3.84605841525058
1999	4.25219375530205
2000	4.68930385042573
2001	5.34296359229204
2002	5.7899187040696
2003	6.07723505459292
2004	6.54160011467474
2005	7.40411964447076
2006	8.255401383757
2007	8.91067732841615
2008	10.1910466765376
2009	11.8916431226815
2010	13.3114045436128
2011	13.7584512962591
2012	13.510342212804
2013	13.8064135001212
2014	12.8270943996361