Year	% of total fuel combustion
1960	23.07692307692308
1961	24.347826086956527
1962	21.7741935483871
1963	22.047244094488192
1964	21.70542635658915
1965	23.571428571428573
1966	21.333333333333332
1967	22.535211267605636
1968	19.463087248322147
1969	21.05263157894737
1970	21.969696969696965
1971	19.41793893129771
1972	18.45885938180235
1973	17.907227615965482
1974	16.71008559732043
1975	14.848379226211224
1976	16.52542372881356
1977	17.29060913705584
1978	18.2097816056598
1979	16.506228765571915
1980	16.594477531131567
1981	16.927522273055622
1982	17.91866028708134
1983	18.09116809116809
1984	17.091660923501035
1985	17.054620880387187
1986	17.50871080139373
1987	17.512690355329948
1988	16.683336667333467
1989	16.74595623215985
1990	12.668582799027194
1991	13.472719141323791
1992	13.419610586452137
1993	14.242824546655456
1994	14.619120957232555
1995	15.684882895670693
1996	16.14801403191128
1997	16.59737417943107
1998	16.66313559322034
1999	16.566327589786173
2000	16.874616485988955
2001	17.08866946915632
2002	16.839858971979957
2003	16.36613429503692
2004	17.199365768171575
2005	17.60417466042514
2006	17.4839935270527
2007	16.89088191330344
2008	18.71128424548183
2009	20.665315992418797
2010	19.47856454720617
2011	18.508608655188457
2012	17.94101279910963
2013	17.921051225896054
2014	18.751609414430654