Year % of total fuel combustion 1971 41.47286821705426 1972 42.04545454545455 1973 45.038167938931295 1974 44.60966542750929 1975 43.51145038167938 1976 40.89219330855019 1977 45.714285714285715 1978 46.50349650349651 1979 51.24999999999999 1980 44.164037854889585 1981 47.49262536873155 1982 38.40304182509506 1983 52.23463687150838 1984 50.144092219020166 1985 48.61538461538461 1986 38.00000000000001 1987 42.16867469879518 1988 45.11494252873563 1989 43.939393939393945 1990 37.79264214046822 1991 62.57668711656442 1992 62.4113475177305 1993 62.04379562043795 1994 57.02479338842975 1995 55.26315789473685 1996 54.78260869565218 1997 54.78260869565218 1998 58.26771653543307 1999 59.199999999999996 2000 0 2001 0 2002 0 2003 0 2004 0 2005 0 2006 0 2007 0 2008 0 2009 0 2010 0 2011 0 2012 0 2013 0 2014 0