Year	% of total fuel combustion
1971	22.678120262758963
1972	22.75918841702581
1973	21.794137094996696
1974	20.271771643449277
1975	20.30630058720838
1976	18.694416768146425
1977	19.176681155714654
1978	22.02571094663031
1979	19.999232275152586
1980	20.0650641604916
1981	19.650505396607848
1982	20.073747329243915
1983	20.609451423343533
1984	19.84008166042872
1985	19.196917865090175
1986	19.299128101945005
1987	18.300015740594997
1988	19.42217091510405
1989	19.336285907609028
1990	18.94146193509251
1991	19.7629297277633
1992	20.913641677407753
1993	19.637650978758856
1994	19.34812966099177
1995	20.46700565292731
1996	20.384678165297352
1997	20.999999999999996
1998	19.712266532054517
1999	21.083682657972364
2000	21.12548218742909
2001	20.654563586500753
2002	20.90707721999255
2003	20.968650272198232
2004	20.680069690503693
2005	20.920005448424817
2006	20.704181804127696
2007	20.70337927058342
2008	20.69567320984241
2009	21.842627684533475
2010	22.57381788147842
2011	23.32834460098742
2012	23.3210770169335
2013	23.88447287582735
2014	22.850307482325515