Year	% of total fuel combustion
1971	29.166666666666668
1972	31.69811320754717
1973	26.937269372693727
1974	30.96085409252669
1975	32.89473684210527
1976	26.436781609195403
1977	15.835777126099707
1978	16.08040201005025
1979	14.794520547945206
1980	18.289085545722713
1981	17.391304347826086
1982	18.91891891891892
1983	20.855614973262032
1984	5.988023952095809
1985	13.114754098360656
1986	12.987012987012989
1987	13.442622950819672
1988	14.052287581699346
1989	13.993174061433445
1990	14.814814814814813
1991	15.053763440860216
1992	15.162454873646208
1993	14.527027027027026
1994	13.915857605177994
1995	13.803680981595093
1996	13.436692506459949
1997	12.761506276150628
1998	10.559006211180124
1999	11.360239162929746
2000	11.69036334913112
2001	11.661341853035143
2002	10.65830721003135
2003	10.097087378640776
2004	9.963099630996311
2005	6.540447504302927
2006	9.41385435168739
2007	7.3873873873873865
2008	8.805031446540882
2009	17.905405405405407
2010	15.619967793880837
2011	15.358361774744028
2012	12.690355329949238
2013	15.046296296296296
2014	14.866310160427807