Year	PPP $ per kg of oil equivalent
1990	3.0141951435995304
1991	3.011488770777562
1992	3.079373666278723
1993	3.0219919500597836
1994	3.073841381471032
1995	3.1228616841512595
1996	3.244377022625843
1997	3.3528678229831144
1998	3.4298548591653772
1999	3.439208089020985
2000	3.622444020545604
2001	3.7204612817839027
2002	3.9526316830412855
2003	4.011485257411617
2004	4.219314817218645
2005	4.511537929630732
2006	4.849204530721016
2007	5.077686715004497
2008	5.125023862731082
2009	5.27357061394767
2010	5.4857442968103305
2011	5.6742311610174605
2012	5.696970791518958
2013	5.969495796225964
2014	6.296483161532319