Year	PPP $ per kg of oil equivalent
1990	2.650883373420085
1991	2.6779807142432666
1992	2.8041159067424046
1993	2.962702147103554
1994	3.211915996790324
1995	3.4454779553587174
1996	3.5359552704615793
1997	3.5417752531237063
1998	3.691426926028289
1999	4.069987498888464
2000	4.071561139601755
2001	4.28742633056541
2002	4.384001801661045
2003	4.48395299955279
2004	4.693150996532053
2005	5.020677075663584
2006	5.326387304137964
2007	5.88242973648695
2008	6.459557382301357
2009	6.880411330183947
2010	6.578061109389379
2011	7.112787703270133
2012	7.216111930515201
2013	7.723853252162537
2014	8.301796274690785
2015	8.782191848320107