Year	PPP $ per kg of oil equivalent
1990	2.9487054560820267
1991	2.91940745615384
1992	3.005412624900866
1993	2.966373410836066
1994	3.0495060677005568
1995	3.027750959305178
1996	3.0816147833593814
1997	3.1211095697245796
1998	3.2156117280367362
1999	3.1668034673127488
2000	3.2741021297449473
2001	3.3773076217178053
2002	3.832777708032602
2003	3.9699748959535595
2004	4.331281864285699
2005	4.574566808114081
2006	4.960294733752798
2007	5.245484408994603
2008	5.543658208981228
2009	6.12332601768789
2010	6.219886596065855
2011	6.320526970909549
2012	6.249768073524322
2013	6.720089565473373
2014	7.247940623512405