Year	% of total fuel combustion
1971	17.264867697144354
1972	17.049515058703417
1973	17.406060606060606
1974	15.81321903902549
1975	15.757978723404259
1976	16.065094930106405
1977	16.52295969520754
1978	18.018196202531644
1979	16.84995340167754
1980	17.927572606669056
1981	19.192634560906516
1982	21.306191687871074
1983	22.91203556684662
1984	24.758842443729904
1985	24.491995073891623
1986	24.055984837439865
1987	24.31862882832256
1988	24.973103819257666
1989	24.993266900080805
1990	22.232103156958647
1991	23.389861086054488
1992	25.875295043273013
1993	27.644836272040298
1994	29.644351464435147
1995	31.12955542835337
1996	31.11944295661489
1997	31.984180410636156
1998	32.40551983691391
1999	33.24999999999999
2000	35.0195938724617
2001	35.442366361586416
2002	36.44458478054942
2003	35.97066073468407
2004	36.26898788189111
2005	36.319512572933334
2006	36.94220562217417
2007	36.933957931477906
2008	37.39319077345375
2009	37.911227154047
2010	37.71485926979214
2011	36.50911797543729
2012	35.21276161723308
2013	33.86682473819403
2014	33.46083926677776