Year	% of total fuel combustion
1971	2.5316455696202533
1972	2.631578947368421
1973	2.2332506203473943
1974	2.699055330634278
1975	3.892617449664429
1976	4.677419354838709
1977	4.239766081871345
1978	4.142857142857142
1979	3.7142857142857144
1980	3.0581039755351687
1981	3.0674846625766876
1982	3.7701974865350087
1983	3.797468354430379
1984	4.21455938697318
1985	5.139186295503212
1986	5.882352941176471
1987	5.970149253731343
1988	6.365503080082135
1989	4.2857142857142865
1990	4.005524861878453
1991	2.7739251040221915
1992	3.2911392405063293
1993	3.8318912237330034
1994	3.8036809815950914
1995	4.0428061831153395
1996	3.990877993158495
1997	3.7946428571428568
1998	3.8054968287526423
1999	3.5934291581108826
2000	3.575076608784474
2001	3.669724770642201
2002	2.4072216649949847
2003	2.4319066147859925
2004	3.0243902439024395
2005	3.404669260700389
2006	3.492333901192504
2007	3.319148936170213
2008	4.845360824742269
2009	5.066666666666666
2010	4.040404040404041
2011	3.8303693570451443
2012	4.366812227074236
2013	3.6885245901639343
2014	3.626220362622037