Year	PPP $ per kg of oil equivalent
1990	3.1871788605081237
1991	3.2805429921138254
1992	3.4868718881254925
1993	3.6353295788442197
1994	3.9098969428615926
1995	4.031541919357405
1996	4.1227972815846625
1997	4.3883947583518905
1998	4.489482648264324
1999	4.669473644841025
2000	4.985290998056049
2001	5.162305613650934
2002	5.4053674471736795
2003	5.4686790320570156
2004	5.756541189924679
2005	6.061365222822164
2006	6.625532155394551
2007	7.159372564228832
2008	7.633572105664608
2009	7.940682594946891
2010	7.902145862767855
2011	8.450496991802684
2012	8.697335146917494
2013	9.23468443242378
2014	9.90595642695108