Year	PPP $ per kg of oil equivalent
1990	5.604646552972699
1991	5.93946274154398
1992	5.989196587415475
1993	6.063665575306994
1994	5.936977029020896
1995	6.063357370225012
1996	6.236917085747765
1997	6.339768649399339
1998	6.449014417852803
1999	6.415988260084028
2000	6.6817812811169235
2001	6.97117718378547
2002	7.170277880826895
2003	7.435081497389134
2004	7.559849628279529
2005	7.917802948871055
2006	8.296891666080349
2007	8.726390174063917
2008	9.141995533333233
2009	9.119799346803289
2010	9.076022040785652
2011	10.02944436847737
2012	10.631075311231676
2013	11.044315760101119
2014	11.396747786965182
2015	11.928868149858218