Year	PPP $ per kg of oil equivalent
1990	9.343413024845006
1991	9.309641818314562
1992	8.053202712468481
1993	8.65281883568157
1994	9.375320507010445
1995	9.769855127263895
1996	10.040355620613935
1997	10.637666370237408
1998	11.593621643511456
1999	11.111695075263443
2000	10.797431933107763
2001	11.35813895127033
2002	11.338612001027222
2003	11.237819454935359
2004	10.171979841705204
2005	10.91170416563084
2006	11.157456590709801
2007	11.505160517717488
2008	12.075155324958683
2009	12.109399051253902
2010	12.676767841761638
2011	13.482179969183294
2012	14.254673023538555
2013	14.83329843044046
2014	15.93059405300142