Year % of total fuel combustion 1971 1.5384615384615377 1972 1.9736842105263157 1973 1.1904761904761898 1974 1.7751479289940828 1975 0.5208333333333331 1976 0.5128205128205132 1977 0 1978 0.4950495049504955 1979 0 1980 0 1981 0 1982 0 1983 2.013422818791946 1984 0 1985 0 1986 0 1987 0 1988 0 1989 0 1990 0 1991 0 1992 0 1993 0 1994 0 1995 0 1996 0 1997 0 1998 0 1999 0 2000 1.6776822785075506E-16 2001 1.5741592340987362E-16 2002 -0.18083182640144665 2003 1.4676171539566897E-16 2004 1.4626673490529572E-16 2005 1.3877787807814457E-16 2006 1.3303094140926435E-16 2007 1.2534129161682133E-16 2008 -0.16286644951140067 2009 2.848478614083427E-16 2010 -0.17182130584192407 2011 -0.1663893510815305 2012 4.610560733493175E-16 2013 -0.1745200698080271 2014 -0.1700680272108845