Year	PPP $ per kg of oil equivalent
1990	4.775976812025183
1991	4.853792507948752
1992	5.0530910239415
1993	5.4563710923304365
1994	5.456471868874837
1995	5.553060984957489
1996	5.626396417147125
1997	5.787748112403029
1998	5.830444770476425
1999	6.132476257948007
2000	6.244945063596647
2001	6.789738691099411
2002	6.944244282818948
2003	7.214282042858701
2004	6.691572377822612
2005	6.951295459339704
2006	7.545274627722575
2007	7.970070312387646
2008	8.882684568862247
2009	8.896868690545286
2010	9.673532508471531
2011	10.196972846844647
2012	9.412617250642485
2013	10.152489871884944
2014	9.82898308148787