Year	% of total fuel combustion
1960	21.132455650705914
1961	21.00681851153344
1962	22.50263396466812
1963	24.171667701363504
1964	22.410181963252732
1965	22.39157770680865
1966	22.289225463309236
1967	22.267858499404927
1968	22.295546500958018
1969	22.65604027584022
1970	23.860250801107664
1971	21.950546328316527
1972	22.12908371518384
1973	21.894976424670077
1974	20.2406013231271
1975	20.728440361329056
1976	20.16481228913933
1977	19.66818835919634
1978	19.87976765460728
1979	19.616910445239007
1980	18.60484195154767
1981	18.364367602227023
1982	18.0485058543065
1983	17.555994144248263
1984	18.949994862988564
1985	19.94568330575821
1986	20.31998616276053
1987	20.09966304669535
1988	19.277612042853136
1989	17.77730131503716
1990	17.20822653168665
1991	18.33755404301344
1992	17.635792561184573
1993	18.09179898069195
1994	16.963227302257845
1995	16.99996665484429
1996	17.994963728253133
1997	17.164757635124577
1998	16.842029120917214
1999	16.85258132999546
2000	16.06425948779823
2001	16.891597081170545
2002	16.25382470419775
2003	16.631710486560692
2004	16.525770384510498
2005	16.609216094817054
2006	16.485826664858266
2007	14.444749862561848
2008	16.024392103056634
2009	16.880885826060393
2010	17.275371377909316
2011	15.673457782009827
2012	16.344141906394697
2013	17.060116568376085
2014	15.459913158803115