Year	% of total fuel combustion
1971	0
1972	0
1973	0
1974	0
1975	0
1976	0.3717472118959108
1977	0.3448275862068966
1978	0.29940119760479045
1979	0.5524861878453038
1980	0.5524861878453038
1981	0.5319148936170214
1982	0.47393364928909953
1983	0.45045045045045046
1984	0.7853403141361256
1985	1.1494252873563218
1986	1.4577259475218658
1987	1.5151515151515151
1988	1.5915119363395225
1989	2.2284122562674096
1990	2.7247956403269757
1991	2.879581151832461
1992	2.6476578411405294
1993	3.3264033264033266
1994	3.339517625231911
1995	4.036697247706423
1996	3.007518796992481
1997	3.5220125786163523
1998	3.878787878787879
1999	4.285714285714286
2000	3.326996197718631
2001	3.173076923076923
2002	3.4639927073837735
2003	3.263598326359833
2004	3.0056864337936635
2005	2.9873039581777445
2006	3.395585738539898
2007	3.248259860788863
2008	3.5478547854785476
2009	3.2006920415224913
2010	3.6290322580645156
2011	3.3401499659168374
2012	3.3623910336239105
2013	4.075691411935954
2014	3.345280764635604