Year	% of total fuel combustion
1971	16.776315789473685
1972	16.514875531268977
1973	15.854738706820196
1974	15.758104375635993
1975	14.729950900163669
1976	14.918032786885247
1977	13.362295945234335
1978	13.184866506389978
1979	12.229516168247022
1980	13.227513227513226
1981	14.777352904897004
1982	14.990328820116055
1983	14.944649446494465
1984	15.717884130982368
1985	18.78876322510033
1986	15.23019593701166
1987	15.002967359050444
1988	22.409232988699205
1989	21.978687333494793
1990	16.21295427115462
1991	15.915915915915916
1992	13.823692478284977
1993	11.685929187305081
1994	15.166058744480706
1995	17.178612059158134
1996	16.453553967657015
1997	27.504873294346975
1998	23.092615259077924
1999	18.21561338289963
2000	18.96183929841195
2001	17.521652231845437
2002	17.67474699929395
2003	17.35501818959983
2004	17.510917030567686
2005	16.903225806451612
2006	16.747114375655826
2007	16.53265346146303
2008	12.631362044096434
2009	8.301886792452832
2010	8.445945945945946
2011	7.3359073359073355
2012	7.379077615298087
2013	8.286731062531773
2014	8.070258723000237