Year	PPP $ per kg of oil equivalent
1990	4.879161568071386
1991	5.073455278200057
1992	5.349108569651124
1993	5.466124702885735
1994	5.729666221635873
1995	5.791083450411705
1996	5.795842381800484
1997	6.048532998604386
1998	6.24242949015458
1999	6.501808054297179
2000	6.839669410211637
2001	6.99997527436505
2002	7.306016521843909
2003	7.310357913056873
2004	7.530601747542059
2005	7.809972321870916
2006	8.468610578001718
2007	9.156874281917439
2008	9.570408920139839
2009	9.901837823490085
2010	9.85687979287193
2011	10.72889752767665
2012	10.968082393286585
2013	11.448526872736029
2014	12.230042384528582
2015	12.409972494523553