Year	PPP $ per kg of oil equivalent
1990	3.43393878471888
1991	3.6193558704681617
1992	3.6772971829711225
1993	3.726237896987625
1994	3.951945743356175
1995	4.086491875121279
1996	4.084107764725235
1997	4.206453528899449
1998	4.365325727159812
1999	4.515272771584564
2000	4.672085740999687
2001	5.0392875180613235
2002	5.171202194590924
2003	5.361579694785262
2004	5.619162564425887
2005	5.874014145231798
2006	6.030636221514804
2007	6.246031434138859
2008	6.29255664756516
2009	6.876238907382988
2010	6.796796737627341
2011	7.3148418018754855
2012	7.688681069211204
2013	8.400285607310158
2014	8.794224198018922
2015	8.44158375289807