Year	PPP $ per kg of oil equivalent
1990	6.247569859757142
1991	5.962155341496849
1992	6.25214788408111
1993	6.434041592209723
1994	6.495723915512471
1995	6.532239369915707
1996	7.0166027359895295
1997	6.651842376879924
1998	6.712539866143893
1999	6.702410890109766
2000	6.625489144780102
2001	6.532405285209139
2002	6.609095668748243
2003	6.557245753289171
2004	6.849217213169358
2005	7.050222739884365
2006	7.220053178555728
2007	7.983601321763436
2008	8.27744103969383
2009	8.704529746747315
2010	8.920754179383243
2011	9.357969105566678
2012	9.707395602252364
2013	10.915590204434501
2014	11.373946557171912