Year	% of total fuel combustion
1971	4.166666666666668
1972	4.150943396226415
1973	3.6900369003690043
1974	3.558718861209963
1975	3.618421052631579
1976	4.0229885057471275
1977	4.69208211143695
1978	4.271356783919599
1979	5.205479452054795
1980	5.309734513274337
1981	6.354515050167225
1982	5.0675675675675675
1983	3.4759358288770055
1984	3.592814371257485
1985	3.934426229508197
1986	3.896103896103896
1987	4.918032786885247
1988	4.901960784313724
1989	5.119453924914675
1990	4.814814814814815
1991	5.017921146953405
1992	4.693140794223827
1993	4.72972972972973
1994	4.53074433656958
1995	4.907975460122701
1996	3.8759689922480614
1997	3.765690376569038
1998	2.8985507246376816
1999	21.524663677130043
2000	21.484992101105842
2001	20.447284345047926
2002	16.77115987460815
2003	16.893203883495143
2004	15.129151291512915
2005	8.605851979345957
2006	15.2753108348135
2007	16.036036036036037
2008	10.53459119496855
2009	3.20945945945946
2010	3.0595813204508855
2011	3.2423208191126283
2012	3.5532994923857872
2013	3.5879629629629637
2014	3.529411764705881