Year	% of total fuel combustion
1971	11.11111111111111
1972	9.333333333333334
1973	13.372093023255815
1974	8.743169398907105
1975	8.837209302325581
1976	8.333333333333332
1977	8.571428571428571
1978	10.714285714285714
1979	10.69364161849711
1980	13.68909512761021
1981	14.828897338403044
1982	16.026711185308848
1983	17.304747320061253
1984	14.40677966101695
1985	16.198125836680052
1986	16.38349514563107
1987	15.092165898617512
1988	14.149821640903685
1989	14.101057579318448
1990	13.978494623655912
1991	12.32583065380493
1992	12.070566388115136
1993	11.8348623853211
1994	14.298093587521665
1995	14.192495921696574
1996	13.75494071146245
1997	13.972809667673717
1998	14.483260553129549
1999	14.462209302325583
2000	15.038115038115038
2001	14.405594405594405
2002	13.70223978919631
2003	14.2761841227485
2004	15.439429928741093
2005	16.28934290447267
2006	16.216216216216218
2007	15.312984997413349
2008	13.994638069705095
2009	13.697219361483008
2010	12.182203389830509
2011	10.38635223281485
2012	9.569798068481123
2013	8.459483526268922
2014	9.78846951472418