Year	% of total fuel combustion
1971	5.014142453072771
1972	5.046511627906977
1973	5.272272464883587
1974	5.299931833674167
1975	5.63152477576827
1976	5.732647814910024
1977	5.9240622140896635
1978	5.987055016181231
1979	5.641454241537823
1980	6.1263705210805925
1981	6.531830238726786
1982	6.776180698151949
1983	6.823912159414397
1984	6.699211415696584
1985	7.076350093109869
1986	7.216648086213301
1987	7.379612257661041
1988	7.576990910324248
1989	7.1301247771836
1990	7.132842621801612
1991	6.841004184100418
1992	7.57935546401745
1993	6.355059623581248
1994	5.573742969864851
1995	5.194698952879581
1996	5.012541306684717
1997	4.572881484573645
1998	5.094176472799732
1999	4.952253308761937
2000	4.79241414659149
2001	5.793735676088616
2002	3.866452835690336
2003	3.3839005821764445
2004	3.416720674011664
2005	3.5436370166407265
2006	3.9967046669041704
2007	4.0944324054009
2008	2.5883125679919545
2009	2.594620328493216
2010	2.6542281071321083
2011	2.32448191631865
2012	2.3448787535632007
2013	2.301599163054852
2014	2.1327482961391175