Year	% of total fuel combustion
1960	2.4448419797257017
1961	3.4734917733089574
1962	3.8316243928764164
1963	4.7313947757516015
1964	4.586330935251802
1965	4.995766299745977
1966	4.954128440366971
1967	5.713319810682895
1968	5.675760426465973
1969	5.4161915621436725
1970	4.990806409246126
1971	3.967409699724385
1972	3.7242616177438754
1973	3.700580751920908
1974	3.6615924014777104
1975	3.554917311344791
1976	3.587896129415922
1977	3.5638284861678446
1978	3.4755612163668204
1979	3.489690721649485
1980	3.329772202501982
1981	3.498585774710019
1982	3.6162115819923395
1983	3.7900926691941885
1984	4.149597238204834
1985	3.7733223493788137
1986	3.3251973075847827
1987	3.2266835856068163
1988	3.491674038738813
1989	3.149070926279514
1990	6.603277194290804
1991	6.581725807731998
1992	6.244503756730488
1993	5.88786715471833
1994	5.774257789977468
1995	4.029030382519572
1996	3.8624615205901147
1997	3.756188441694367
1998	3.3249522634818605
1999	3.564424664417486
2000	3.430233525396094
2001	3.570001080263584
2002	3.352312309795561
2003	3.3283686281032554
2004	3.4668388806409416
2005	3.3945528206486735
2006	3.27668820675
2007	3.102839421710044
2008	3.2965153314406597
2009	3.6445054089073134
2010	3.235668743249886
2011	2.810500316746268
2012	2.926206702912424
2013	2.745444301487593
2014	2.73427481341649