Year	PPP $ per kg of oil equivalent
1990	4.75660409955456
1991	5.166097128672671
1992	5.010045145988855
1993	5.522233817187914
1994	4.7515996343043625
1995	5.375471431196809
1996	5.125404609548181
1997	5.570769388854333
1998	5.365879361004857
1999	5.367186999754481
2000	5.538027288567978
2001	5.657751765695372
2002	4.8249473637732345
2003	4.935358434357848
2004	5.627286061980607
2005	6.4155618150499745
2006	6.52242714064374
2007	7.876809285520054
2008	7.557597906933012
2009	7.345304667890549
2010	6.579339992304972
2011	7.535064485434673