Year	PPP $ per kg of oil equivalent
1990	3.8120011556950395
1991	3.9391033748248416
1992	4.095571381549576
1993	4.198562741271443
1994	4.3646364624410365
1995	4.484761425150341
1996	4.586620889551679
1997	4.78362173470156
1998	4.96033972854062
1999	5.111029059312406
2000	5.344496131237297
2001	5.576390839937368
2002	5.760348752567962
2003	5.898961642411661
2004	6.133407856616214
2005	6.454959877007002
2006	6.929844327273018
2007	7.287549498761981
2008	7.6201092615195325
2009	7.825666657857426
2010	7.859379182769752
2011	8.368254914427224
2012	8.720237976539828
2013	9.063755827963991
2014	9.413477338660739
2015	9.782515252115383