Year	PPP $ per kg of oil equivalent
1990	3.8827084312673064
1991	3.912871940658684
1992	4.019018439228819
1993	4.1734113491735005
1994	4.146401454783708
1995	4.258326072822685
1996	4.106723748701141
1997	4.29584012747978
1998	4.34910947754108
1999	4.532715924349728
2000	4.901452690303265
2001	5.111018499015105
2002	5.617485260393883
2003	5.533888890409605
2004	5.732888823842482
2005	5.971955627527529
2006	6.445304407154172
2007	6.895219323795648
2008	6.945122559357352
2009	7.26408234469501
2010	7.190790467159733
2011	8.040029630930597
2012	8.727863834722099
2013	8.73865737834371
2014	9.542815325380763
2015	9.85558942172235