Year	% of total fuel combustion
1971	21.465968586387437
1972	21.39303482587065
1973	20.673076923076923
1974	19.724770642201833
1975	20.346320346320347
1976	19.574468085106382
1977	18.326693227091635
1978	16.600790513833992
1979	16.7420814479638
1980	16.894977168949772
1981	17.712177121771216
1982	11.688311688311689
1983	10
1984	17.67955801104972
1985	8.61244019138756
1986	11.210762331838566
1987	12.06896551724138
1988	11.715481171548117
1989	11.363636363636363
1990	11.811023622047244
1991	12.719298245614036
1992	12.686567164179104
1993	12.867647058823529
1994	13.945578231292515
1995	14.018691588785048
1996	13.96011396011396
1997	14.166666666666666
1998	10.622710622710622
1999	11.262798634812286
2000	13.654618473895583
2001	11.861313868613138
2002	12.406576980568012
2003	12.792511700468017
2004	15.202702702702704
2005	14.687499999999998
2006	13.161290322580646
2007	12.395709177592371
2008	12.757731958762886
2009	14.270270270270272
2010	12.057416267942585
2011	13.308687615526802
2012	12.920908379013312
2013	12.454212454212453
2014	12.585812356979407