Year	% of total fuel combustion
1971	50
1972	55.17241379310346
1973	51.515151515151516
1974	47.5
1975	50
1976	46.93877551020408
1977	42.85714285714285
1978	41.66666666666667
1979	39.34426229508197
1980	42.10526315789474
1981	41.37931034482759
1982	43.39622641509434
1983	39.34426229508197
1984	36.92307692307692
1985	39.34426229508197
1986	40.78947368421053
1987	43.209876543209866
1988	41.11111111111111
1989	41.584158415841586
1990	37.931034482758626
1991	36
1992	37.878787878787875
1993	36.734693877551024
1994	36.42384105960265
1995	34.83870967741935
1996	33.54037267080746
1997	32.71604938271605
1998	29.608938547486037
1999	32.272727272727266
2000	30.864197530864196
2001	29.296875
2002	29.88505747126437
2003	29.454545454545457
2004	29.96389891696751
2005	29.054054054054053
2006	26.363636363636367
2007	24.483775811209437
2008	24.207492795389047
2009	25.438596491228072
2010	25.136612021857925
2011	25.549450549450547
2012	25.737265415549597
2013	25.587467362924283
2014	25.5050505050505