Year	PPP $ per kg of oil equivalent
1990	4.078972826102516
1991	3.9663206502968023
1992	3.9513055484633024
1993	4.094515522016484
1994	4.276023066138831
1995	4.494817703573313
1996	4.779591569159965
1997	4.829700085285768
1998	5.037264408295775
1999	5.390711034126559
2000	5.600623618955132
2001	5.845293160911082
2002	5.77065811612018
2003	5.894699058463639
2004	6.096333612525246
2005	6.452046447609184
2006	6.992528248977752
2007	7.423163623538485
2008	7.739640321557878
2009	7.487094786145609
2010	7.845289433601899
2011	8.22831233558653
2012	8.093511839379357
2013	8.009639071714494
2014	8.393957198013705