Year	constant 2011 PPP $ per kg of oil equivalent
1990	4.38323478096175
1991	4.49979640407848
1992	4.52130927561073
1993	4.67527865494851
1994	4.66825607141313
1995	4.84416626417896
1996	4.33991276814958
1997	4.42285894194569
1998	4.66130879329775
1999	4.70713987166767
2000	5.77094723161089
2001	5.71568434924157
2002	5.57572691796476
2003	5.46880220466947
2004	5.47027816286698
2005	5.54436019128684
2006	4.88427098784435
2007	4.7613135170889
2008	4.88560738493617
2009	4.76497662443119
2010	4.57973321111084
2011	4.58926767377526
2012	4.64359608440662
2013	4.76216891921755
2014	4.80109793770648