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	7.276598638744004
1972	7.153571867699494
1973	7.223623917036158
1974	7.001009611321879
1975	6.923408385249501
1976	6.631831726689071
1977	6.538210365917884
1978	6.309031563163978
1979	6.427581699757123
1980	5.987729225740147
1981	6.264736933379173
1982	6.266872969028319
1983	6.321271791064504
1984	6.387198031771618
1985	5.963526416131137
1986	5.725047453337552
1987	5.527618321036815
1988	5.35176458082347
1989	4.985943407862335
1990	6.138741902569821
1991	5.9884780250450245
1992	5.366366519943246
1993	5.502659953450816
1994	5.233314865402435
1995	4.416561559714355
1996	3.6686705495467
1997	3.9613626898033023
1998	3.754825373277289
1999	3.9362318003171293
2000	3.20128670486794
2001	3.2115292034848513
2002	3.113881308938405
2003	3.1163736876919272
2004	3.113193996462608
2005	3.0334263365806335
2006	2.9262053381092725
2007	2.822442349348315
2008	2.7897241911646407
2009	2.877923372465174
2010	2.6651563269576477
2011	2.3954910042889765
2012	2.5165210932824253
2013	2.449910918358776
2014	2.4620206947435874