Year	constant 2011 PPP $ per kg of oil equivalent
1990	4.81758049254779
1991	4.61368736206386
1992	4.64378068526741
1993	4.47733234682869
1994	4.50658511527213
1995	4.38254688138707
1996	4.38031925255456
1997	4.36125107246191
1998	4.4433652584074
1999	4.31486197280334
2000	4.36224613678816
2001	4.40066257771249
2002	4.91772309237711
2003	4.99513699982694
2004	5.30703308694375
2005	5.43472202597905
2006	5.71668508986442
2007	5.88589883812937
2008	6.10289129447045
2009	6.69971229201542
2010	6.72365045119898
2011	6.69433056836372
2012	6.62463068736377
2013	7.0429880990529
2014	7.44807998890939