Year	% of total fuel combustion
1960	6.685432793807176
1961	7.430997876857745
1962	7.416719044626019
1963	6.986899563318774
1964	6.529044647143545
1965	5.788590604026845
1966	5.375939849624059
1967	5.490483162518299
1968	5.1679586563307485
1969	4.748757592490339
1970	3.731343283582089
1971	3.7901606425702803
1972	3.464097270016058
1973	3.235232728031724
1974	3.3944331296673456
1975	3.531808920081504
1976	3.27445921809883
1977	3.5592881423715244
1978	3.405346027096301
1979	3.308687615526801
1980	3.008204193254331
1981	3.6020206457280928
1982	3.9255729521216254
1983	3.8037097910307605
1984	3.937187073281747
1985	3.7290242386575523
1986	3.798513625103222
1987	3.7186122292505277
1988	3.9642440730664577
1989	4.039619343561856
1990	3.9204756596060952
1991	3.299725022914759
1992	3.784514385016414
1993	3.673700075357951
1994	2.8547439126784218
1995	3.0341113105924586
1996	2.7987775454399224
1997	2.8262676641729008
1998	3.0633802816901423
1999	2.981610426709517
2000	4.4546287809349225
2001	4.743017683027598
2002	4.3581994592015265
2003	4.287320775934776
2004	3.7887828162291166
2005	4.452554744525547
2006	3.3785822021116143
2007	3.747473176799876
2008	4.257602862254025
2009	4.186915887850468
2010	3.8480194017784966
2011	3.930933137398971
2012	4.491386382280557
2013	4.274716369529983
2014	4.265193370165746