Year	constant 2011 PPP $ per kg of oil equivalent
1990	12.0447905999722
1991	12.3451238250816
1992	12.5162870494677
1993	12.5942456310095
1994	13.3500873812831
1995	13.0234174015666
1996	13.5098408130424
1997	13.8959849171636
1998	13.8495134713935
1999	13.5804295358355
2000	13.2541867378342
2001	13.0453822413472
2002	13.3688961716012
2003	13.5042538793139
2004	13.8375136390806
2005	13.6165373099479
2006	13.3543805590237
2007	14.0400472949564
2008	14.4616592787717
2009	15.3142450644946
2010	15.1296990430859
2011	15.7205652683948
2012	16.008275938693
2013	16.1034190078455
2014	16.4256845768048