Year	PPP $ per kg of oil equivalent
1990	4.869414792736827
1991	5.088398629533333
1992	5.4430832187130855
1993	5.615717640542773
1994	5.779200124393497
1995	6.413312426613998
1996	6.557251651129818
1997	6.951959492027656
1998	7.34216125582814
1999	7.629342597384892
2000	8.32963101183287
2001	8.772533435258067
2002	9.620029707760237
2003	10.322655241500929
2004	10.88631488330863
2005	11.549760042614613
2006	12.917647172355526
2007	13.69545149861239
2008	13.409423593985988
2009	13.166845517732154
2010	13.706505799668706
2011	15.74558042282789
2012	16.22245940700776
2013	16.97955367504543
2014	18.68954980177756
2015	24.545201859718684