Year	constant 2011 PPP $ per kg of oil equivalent
1990	1.71785908771958
1991	1.43905040066421
1992	1.64741673434523
1993	2.83051073145284
1994	4.74491003155624
1995	4.25171514773449
1996	4.15630488655184
1997	4.10800334624291
1998	4.32780913809518
1999	4.62381634200608
2000	4.45635335057069
2001	4.90378522795108
2002	5.93308666704135
2003	6.40809903803725
2004	6.6952052416466
2005	6.35648772365208
2006	7.0652602360966
2007	7.20773632726705
2008	7.31720160605172
2009	7.23035741765
2010	7.76666016958062
2011	7.43587664887042
2012	7.28692821443096
2013	7.70967213305023
2014	7.82962685901227