Year	% of total fuel combustion
1971	18.282513208988476
1972	17.71965371154909
1973	16.963685272360458
1974	15.310307609282244
1975	15.440705522983691
1976	13.628816529840421
1977	13.2007732670533
1978	15.002568053415514
1979	12.740263661064708
1980	12.275650254343025
1981	12.09953060201431
1982	12.2436698606675
1983	12.602173285892876
1984	12.571480439321048
1985	11.85125375678464
1986	11.875142401458191
1987	11.708065272037834
1988	12.290095956134339
1989	12.223958113414685
1990	12.115495037322615
1991	12.38897268309033
1992	12.770838643894978
1993	12.445432830903549
1994	12.625936971064721
1995	13.539942252165543
1996	12.727205282290974
1997	12.400535173579327
1998	11.94985786210912
1999	12.889229198570701
2000	12.541442372820931
2001	11.37548582804057
2002	11.256961018297535
2003	11.190236898779613
2004	10.987401113389978
2005	11.601171130033038
2006	11.856883089100439
2007	12.45146127120376
2008	11.521466884052835
2009	11.706975113915176
2010	11.820819196538329
2011	12.796857179064759
2012	12.381956879001201
2013	13.058679013512236
2014	12.049294647552417