Year	PPP $ per kg of oil equivalent
1990	1.8390166961373084
1991	1.6582637722301847
1992	1.5267655529584467
1993	1.7050787091099846
1994	1.7180215283239608
1995	1.791898799567396
1996	2.1124496871952183
1997	2.509560236868202
1998	2.499501245774599
1999	2.850861696525941
2000	3.222904764691093
2001	3.8638358370520187
2002	3.7448603871669084
2003	3.8479238780302487
2004	3.6753086831582564
2005	4.151005552876606
2006	3.923363076412239
2007	4.078969499233434
2008	4.062675915022687
2009	4.55303628750233
2010	4.540876492647635
2011	4.448777734613655
2012	5.006037985159329
2013	5.114398119729258
2014	5.56749147884709