Year	PPP $ per kg of oil equivalent
1990	3.6956219818245915
1991	4.115486883614799
1992	4.489182310040023
1993	4.948176729045484
1994	4.403951003037429
1995	4.748160985188108
1996	4.999407176774191
1997	5.889715890368523
1998	6.143317593069715
1999	5.785546417013093
2000	6.656240361081075
2001	6.919627377287824
2002	6.861814224705611
2003	7.650751085950086
2004	8.263408862413907
2005	8.838146500936833
2006	9.03588551715465
2007	10.147356616111663
2008	10.570671626201511
2009	9.997343150463513
2010	10.285589845732005
2011	10.192043483000175
2012	9.566700344109798
2013	9.621312778711822
2014	11.036506454766657