Year	constant 2011 PPP $ per kg of oil equivalent
1990	8.97948092550535
1991	9.47406838703486
1992	8.46102557920663
1993	8.59737221018471
1994	9.04150880135658
1995	9.44913671097738
1996	10.2498380752873
1997	10.582386231488
1998	9.41623464315135
1999	9.99979453960963
2000	9.81080526893436
2001	9.72145389434847
2002	10.1511211412291
2003	10.65506211731
2004	11.1281190169676
2005	11.2746930834581
2006	11.8219096766569
2007	12.3856897241962
2008	12.4348768761277
2009	12.3110844161406
2010	12.2105521410687
2011	13.478338180781
2012	12.4140743657105
2013	13.0697757445107
2014	12.4364010090215