Year	% of total fuel combustion
1971	4.473269487210571
1972	4.393105099353602
1973	4.443426477324782
1974	4.809894640403115
1975	5.105633802816899
1976	5.328557035710286
1977	4.98924731182796
1978	5.415357955160836
1979	5.633658286300669
1980	5.432384154670589
1981	5.586889432797699
1982	5.860726643598616
1983	5.6165540540540535
1984	5.259203606311045
1985	7.441595441595443
1986	4.935199585277345
1987	5.191337881934144
1988	4.841887960964622
1989	4.250644760722133
1990	4.608573153552024
1991	4.877815960290189
1992	5.320446654780896
1993	5.786433097279165
1994	6.370757180156657
1995	6.624605678233437
1996	6.59349463227047
1997	6.1620795107033635
1998	5.681146572104019
1999	5.5994256999282115
2000	5.4191788687912705
2001	5.534854836205559
2002	5.887673711043501
2003	6.429172081645134
2004	6.954207329557087
2005	7.207388074683798
2006	6.3008002016256075
2007	5.4055686416621365
2008	7.161052929521652
2009	7.147509918872505
2010	5.986645176145521
2011	4.8128932553261965
2012	4.833234549275282
2013	5.536810664306657
2014	6.465360428252172