Year	% of total fuel combustion
1971	20.141748874628863
1972	20.46351931330472
1973	19.884994949102495
1974	19.818885662933777
1975	19.877825290164935
1976	19.54802863553799
1977	19.450812076281522
1978	19.02712209571415
1979	19.284196764177153
1980	18.486551585708554
1981	17.98831385642738
1982	17.44800604022239
1983	17.960348452988885
1984	17.90099121423744
1985	17.528659024260197
1986	16.472011784511782
1987	16.699498790614168
1988	16.110830992340752
1989	16.942669426694266
1990	15.930303558967202
1991	16.039624608967678
1992	17.07750515936712
1993	16.72067401166559
1994	18.34174212302449
1995	18.217577166263023
1996	19.293491105613942
1997	18.819253612268415
1998	18.951661999269447
1999	18.423755171503185
2000	18.937356696011552
2001	18.077535847052577
2002	18.73775141825683
2003	18.395035362988832
2004	18.889163343801826
2005	18.479751049985857
2006	18.63381835591915
2007	18.924445863176587
2008	17.756928572800433
2009	17.260439449818346
2010	16.354059377315195
2011	16.466910779673125
2012	15.436920046309899
2013	15.959541103794718
2014	15.307928510862496