Year	constant 2011 PPP $ per kg of oil equivalent
1990	5.00050834674509
1991	5.25093532683197
1992	5.32587045668187
1993	5.33214217093783
1994	5.41626459124794
1995	5.4464765337905
1996	5.58427855940704
1997	5.7325709985495
1998	5.76767966939256
1999	5.84132411033089
2000	5.95780428867054
2001	6.05343840925435
2002	6.08655840659119
2003	5.96614538261833
2004	5.81459899029413
2005	5.85707730149405
2006	5.94009888823849
2007	6.10475392257244
2008	6.2976724020105
2009	6.29066180813262
2010	6.25403384557666
2011	6.38862544417205
2012	6.57580981288632
2013	6.75611456234595
2014	7.00466154244245