Year	PPP $ per kg of oil equivalent
1990	3.1138303758434405
1991	3.1897217578582855
1992	3.31088469240552
1993	3.422699968551055
1994	3.569922321059927
1995	3.6954895293856267
1996	3.8202350628127726
1997	4.018497040752212
1998	4.210013542279281
1999	4.35622945597141
2000	4.509195008900476
2001	4.743760812799978
2002	4.844583932093877
2003	5.066603676137673
2004	5.293944664280405
2005	5.623322678731804
2006	6.015078939718524
2007	6.193503400201201
2008	6.486315179413665
2009	6.687883944193093
2010	6.793432003026023
2011	7.12180686580145
2012	7.535536360896784
2013	7.734268035933118
2014	7.9452415249550565
2015	8.383338720743625