Year	% of total fuel combustion
1971	7.044025157232705
1972	7.0564728152276786
1973	6.5684962070504245
1974	6.133508498234667
1975	5.9272979856448265
1976	5.7672142607479895
1977	5.670138179837996
1978	5.635034672330855
1979	5.783516094800141
1980	6.153479220082284
1981	6.784000000000001
1982	7.438704308302927
1983	8.026440037771481
1984	7.68919738526855
1985	7.913945447560508
1986	7.491558404395353
1987	7.800390298299415
1988	8.511921074266922
1989	8.538303174775166
1990	8.938941655359566
1991	8.735680284563479
1992	8.814061621787337
1993	8.748151798915723
1994	8.940114068441066
1995	8.629018092394167
1996	8.034153283187639
1997	7.635851998326803
1998	7.568926010791634
1999	7.695608639679588
2000	7.320994834251309
2001	7.2305684745876135
2002	7.184062248457203
2003	6.5731874145006834
2004	6.369241695451465
2005	6.177133655394525
2006	6.1045123077413
2007	6.0217206649678445
2008	5.728822328897065
2009	6.042296072507552
2010	5.346395703451813
2011	5.159270001796761
2012	4.746115953012504
2013	4.508895929807458
2014	4.289735725389689