Year	PPP $ per kg of oil equivalent
1990	3.5795602905652846
1991	3.7115785162612993
1992	3.8613795113464056
1993	3.964231475043282
1994	4.1601718553697
1995	4.293108801300013
1996	4.3875439464115
1997	4.599646646413434
1998	4.764194550270942
1999	4.896172757298018
2000	5.13672745877345
2001	5.3312140819040215
2002	5.506874103594655
2003	5.665912091065183
2004	5.919527477544118
2005	6.246515406843545
2006	6.7090666469344935
2007	7.071830333323073
2008	7.4138786441383475
2009	7.5855715087138895
2010	7.616385393813212
2011	8.10140222679403
2012	8.385934481353107
2013	8.7239032629125
2014	9.026612532446341
2015	9.855839392969543