Year	% of total fuel combustion
1960	18.843075676223282
1961	17.21860137396512
1962	17.898506552880217
1963	19.846069268829027
1964	18.07973757254605
1965	18.0466472303207
1966	19.71703150026695
1967	19.808598634221408
1968	19.839732300105673
1969	21.476236979166668
1970	22.613888787735334
1971	23.200829588662284
1972	23.80315243285579
1973	22.68569337724113
1974	22.097129576529532
1975	23.316716097684107
1976	22.34020769343279
1977	20.708635365596898
1978	22.513677362117406
1979	21.38213680045223
1980	20.364844321828727
1981	19.963565913888328
1982	19.74313110283553
1983	20.391352187230503
1984	21.241992570275254
1985	20.653350100897846
1986	20.418451496342918
1987	19.517912794064923
1988	18.58740114535042
1989	17.82798606416723
1990	17.19797580210126
1991	18.8121361973935
1992	17.660479104013273
1993	17.701311595338872
1994	15.645647232940432
1995	16.397326549952616
1996	16.955582353532307
1997	16.20051849636055
1998	16.684073741225617
1999	17.459291187739463
2000	16.456900858889867
2001	17.35466361948293
2002	16.140589144382524
2003	16.547974748949745
2004	16.602180794934927
2005	17.593302798536083
2006	16.630294392731486
2007	15.502786966964246
2008	16.893688482530205
2009	19.076666405985247
2010	19.42636964454311
2011	18.325043618655766
2012	18.972666266572098
2013	20.454006638217166
2014	18.06637265021426