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	6.76952667670179
1972	6.743599461557561
1973	6.752103114084716
1974	6.723591611976787
1975	6.6527900514251055
1976	6.477258969288512
1977	6.31217553048741
1978	5.996080436264486
1979	6.017647789883592
1980	5.86924097467718
1981	6.025240873931334
1982	6.02230275551582
1983	5.989489262034327
1984	5.9567405894368255
1985	5.700094522374487
1986	5.629776900268987
1987	5.501133537510228
1988	5.163924103124895
1989	4.853127478954784
1990	5.449336024920832
1991	5.239325955557966
1992	4.647283974983256
1993	4.902657085561498
1994	4.53278861960644
1995	4.297808393070491
1996	3.341837523579801
1997	3.7574382365880195
1998	3.5996288853917036
1999	3.7847278824433523
2000	2.78582878369346
2001	2.753613399002318
2002	2.754692881606552
2003	2.7967236325229066
2004	2.757856551126735
2005	2.6447583141072535
2006	2.569900787255206
2007	2.5401871707100376
2008	2.463465779282417
2009	2.417286204947612
2010	2.294141678107902
2011	2.2017443418520233
2012	2.2582167360757412
2013	2.249141233020825
2014	2.2881697095274025