Year	% of total fuel combustion
1960	13.157894736842103
1961	11.334289813486368
1962	11.392405063291136
1963	10.411311053984573
1964	9.842041312272174
1965	9.851088201603664
1966	10.280373831775702
1967	9.913793103448278
1968	9.64102564102564
1969	9.542356377799416
1970	8.59375
1971	6.601806810284919
1972	7.290233837689135
1973	7.041383570105002
1974	6.067961165048544
1975	5.660377358490567
1976	4.395036194415718
1977	4.586666666666666
1978	5.11392405063291
1979	4.616087751371115
1980	4.212299915754001
1981	3.940490550864494
1982	4.100946372239748
1983	4.487917146144995
1984	4.63443867359169
1985	5.058528428093645
1986	4.552129221732745
1987	4.396396396396395
1988	4.367417677642981
1989	3.474279558308645
1990	3.9334741288278776
1991	3.8237528488224863
1992	3.3692413476965397
1993	3.3810753698051177
1994	3.318181818181818
1995	3.0283778060144013
1996	5.183061314512571
1997	4.117398648648649
1998	3.458213256484151
1999	3.2208326194963166
2000	3.6652835408022124
2001	2.4593003117422936
2002	2.059014267185473
2003	2.1265377855887517
2004	2.7361899845121327
2005	2.541958611699528
2006	2.108807371965267
2007	2.30684730867814
2008	2.139341158652025
2009	2.0731247644176407
2010	2.5657202944269186
2011	2.38095238095238
2012	2.2777047744196226
2013	2.538303224331123
2014	2.686288250408783