Year	PPP $ per kg of oil equivalent
1990	6.927049177981296
1991	7.407945408369331
1992	7.22196697567672
1993	7.5192764431426244
1994	7.72859694842812
1995	7.858507539803793
1996	7.971532391318338
1997	7.88042048828388
1998	7.992132674382229
1999	8.171194966299202
2000	8.161653278129275
2001	8.053971231785619
2002	8.060117752204555
2003	8.933081902057406
2004	8.970250263694425
2005	9.45878938031902
2006	9.952393286951924
2007	9.796987774310956
2008	9.92030994220885
2009	8.551620406975282
2010	8.780913524875166
2011	8.576405724279546
2012	9.141417979495857
2013	10.227561743663284
2014	10.204658284765216