Year % of total fuel combustion 1971 34.12043947439255 1972 34.96254423456959 1973 34.96300927373137 1974 35.65590802050146 1975 36.76419163072619 1976 36.64051432930151 1977 36.08897223524509 1978 36.149242079240125 1979 36.026889833996435 1980 35.516605166051654 1981 36.76256690714452 1982 36.438478618183915 1983 35.343469877390014 1984 35.0783361916112 1985 34.57378315735256 1986 34.69059627038986 1987 34.15213525493006 1988 34.00366581304353 1989 34.09076666624889 1990 35.570232040284424 1991 35.886988883753745 1992 35.742434821713864 1993 36.3486124819244 1994 36.01665887367746 1995 36.40164699889634 1996 36.185215888774586 1997 35.39197533765051 1998 35.212348242090535 1999 35.2817190565263 2000 34.418796011800026 2001 34.51469294233467 2002 34.50368142423743 2003 34.4092440199548 2004 34.88017888102143 2005 35.06302010211844 2006 35.19304768243331 2007 35.702184640196506 2008 35.38201177590522 2009 35.808437757446995 2010 35.842534415095884 2011 36.48913500999684 2012 37.01348723259162 2013 36.57130003936294 2014 36.93517544992284