Year	PPP $ per kg of oil equivalent
1990	4.376395119479216
1991	4.576282873597168
1992	4.839270449065648
1993	4.939270426380824
1994	5.209800904881979
1995	5.282282147250621
1996	5.2916054587861385
1997	5.547411142160072
1998	5.788700403745018
1999	6.0844291109842255
2000	6.438766350169663
2001	6.592291979782836
2002	6.889193611146198
2003	6.908568314807854
2004	7.169496310829819
2005	7.436551079766295
2006	8.049083634489849
2007	8.731812564648742
2008	9.195042141042908
2009	9.579422255197805
2010	9.531331468948977
2011	10.342114123929544
2012	10.634053090618673
2013	11.122874286776606
2014	11.866984739892466
2015	12.113566186463508