Year	% of total fuel combustion
1971	22.67812026275897
1972	22.759188417025808
1973	21.794137094996696
1974	20.271771643449277
1975	20.30630058720838
1976	18.694416768146425
1977	19.176681155714654
1978	22.025710946630312
1979	19.999232275152586
1980	20.065064160491602
1981	19.650505396607848
1982	20.07374732924392
1983	20.609451423343536
1984	19.84008166042872
1985	19.196917865090175
1986	19.299128101945005
1987	18.300015740594997
1988	19.422170915104054
1989	19.336285907609025
1990	18.94146193509251
1991	19.762929727763293
1992	20.91364167740775
1993	19.637650978758852
1994	19.34812966099177
1995	20.467005652927305
1996	20.384678165297352
1997	21.000000000000004
1998	19.712266532054517
1999	21.083682657972364
2000	21.125482187429096
2001	20.654563586500753
2002	20.907077219992548
2003	20.96865027219824
2004	20.680069690503693
2005	20.920005448424824
2006	20.704181804127696
2007	20.703379270583422
2008	20.695673209842415
2009	21.842627684533475
2010	22.57381788147842
2011	23.32834460098743
2012	23.3210770169335
2013	23.884472875827345
2014	22.850307482325515