Year	PPP $ per kg of oil equivalent
1990	3.0141951435995296
1991	3.0114887707775613
1992	3.0793736662787237
1993	3.0219919500597845
1994	3.07384138147103
1995	3.1228616841512604
1996	3.2443770226258444
1997	3.3528678229831157
1998	3.4298548591653764
1999	3.439208089020986
2000	3.6224440205456023
2001	3.7204612817839027
2002	3.952631683041287
2003	4.011485257411618
2004	4.219314817218646
2005	4.511537929630732
2006	4.849204530721016
2007	5.077686715004496
2008	5.125023862731082
2009	5.27357061394767
2010	5.485744296810329
2011	5.67423116101746
2012	5.69697079151896
2013	5.969495796225963
2014	6.29648316153232