Year	% of total fuel combustion
1960	5.405405405405406
1961	5.623242736644799
1962	5.970149253731344
1963	5.985267034990791
1964	5.918189730200173
1965	6.446140797285836
1966	6.7268252666119785
1967	7.154742096505824
1968	7.465135356849878
1969	7.58513931888545
1970	6.864161849710982
1971	6.592592592592592
1972	5.171299288946348
1973	5.209580838323354
1974	4.140310523289249
1975	4.26049908703591
1976	3.795379537953795
1977	3.7927350427350426
1978	3.953871499176278
1979	4.3398533007334965
1980	4.189435336976323
1981	4.184615384615385
1982	4.3478260869565215
1983	4.208194905869324
1984	4.229934924078091
1985	3.9682539682539675
1986	3.9149888143176734
1987	3.502352326189231
1988	3.1357177853993146
1989	3.4583536288358503
1990	5.519779208831648
1991	4.986400725294652
1992	5.04201680672269
1993	5.209222886421861
1994	5.3962900505902205
1995	5.641454241537819
1996	5.613472333600641
1997	5.445180279617365
1998	5.728191688506177
1999	5.620775524724297
2000	5.246807041767346
2001	4.876483798524222
2002	5.373230373230373
2003	5.398847437063997
2004	4.933703361085414
2005	5.192878338278931
2006	5.272511848341232
2007	5.2744556884391285
2008	4.902840059790732
2009	4.694681549573211
2010	4.678747940691927
2011	5.396290050590218
2012	5.639218199295098
2013	5.394056847545219
2014	5.057618437900128