Year	PPP $ per kg of oil equivalent
1990	3.1860745302937765
1991	3.0555575478422634
1992	3.207353405230793
1993	3.109396323200894
1994	3.0918670808319733
1995	3.4570964737252043
1996	3.308095310977193
1997	3.4715063035356564
1998	3.7309006282225026
1999	3.941350285227085
2000	4.277752689249178
2001	4.337160179684555
2002	4.251285760295263
2003	4.105270701578119
2004	4.373268430143944
2005	4.884438437206584
2006	4.8447106348921505
2007	5.426162495325838
2008	6.010294706138755
2009	6.057649684814773
2010	5.703757200074034
2011	6.258658397942522
2012	6.512840505040686
2013	6.784107203614538
2014	6.720585512890074
2015	7.172971472445263