Year	PPP $ per kg of oil equivalent
1990	4.714588564961969
1991	4.563005248781671
1992	4.7512171465830315
1993	4.772074696634877
1994	4.935063386310141
1995	4.465981680606497
1996	4.497606976302384
1997	4.6157441141489475
1998	4.934509549981926
1999	5.268565782971396
2000	5.583561070925806
2001	5.605784658160008
2002	5.910878728995367
2003	6.09597348161746
2004	6.373660479544431
2005	6.5424318702241635
2006	7.0486164399049
2007	7.591439795795004
2008	7.716239214574013
2009	7.876184218782021
2010	7.773543280593178
2011	8.10861011114737
2012	8.482032641482414
2013	8.99843550127358
2014	9.538866522037702
2015	9.962052438329945