Year	constant 2011 PPP $ per kg of oil equivalent
1990	1.98431960373431
1991	2.2268714816197
1992	2.45979934635833
1993	2.64417759800914
1994	2.85417851916779
1995	2.94935795851839
1996	3.15444772472626
1997	3.44926440110287
1998	3.69424445140843
1999	3.90206879070477
2000	4.10458212374195
2001	4.27295974011909
2002	4.36858251800654
2003	4.20641376119701
2004	4.06077461042204
2005	4.09186774740809
2006	4.21890505459328
2007	4.45601100018418
2008	4.73705831084195
2009	4.85063534210761
2010	4.85904238139724
2011	4.96312519086168
2012	5.15742960269783
2013	5.38432835038502
2014	5.6891487235341