Year	PPP $ per kg of oil equivalent
1990	3.8551100825428604
1991	4.107545319083889
1992	4.0187392110852
1993	3.919678089103594
1994	4.119531883227319
1995	4.206239055408289
1996	4.253173252590025
1997	4.2192807294579024
1998	4.433474678364011
1999	4.53180517496037
2000	4.631615793213325
2001	4.890370957514668
2002	5.130550324062869
2003	5.21930718866526
2004	5.487110960787119
2005	5.771219785841404
2006	6.092714358313398
2007	6.366921263708004
2008	6.468145557451179
2009	6.34620820548044
2010	6.290101178913962
2011	6.239088623913613
2012	6.39363657107372
2013	6.545572713547815
2014	6.67851305035338
2015	7.001656166827866