Year % of total 1960 100 1961 100 1962 100 1963 100 1964 100 1965 100 1966 100 1967 100 1968 100 1969 100 1970 100 1971 100 1972 100 1973 100 1974 100 1975 100 1976 100 1977 100 1978 100 1979 100 1980 100 1981 100 1982 100 1983 100 1984 100 1985 100 1986 100 1987 100 1988 100 1989 100 1990 100.84250000000002 1991 93.71222222222222 1992 70.28416666666666 1993 85.56333333333333 1994 86.43642857142856 1995 85.56333333333333 1996 88.008 1997 82.5075 1998 84.92 1999 86.85 2000 91.67500000000001 2001 85.56333333333332 2002 81.31173913043477 2003 86.09478260869565 2004 88.00800000000001 2005 88.00800000000001 2006 88.00800000000001 2007 75.78466666666667 2008 103.34272727272729 2009 31.48434343434343 2010 88.00800000000001 2011 86.09478260869565 2012 63.25575 2013 95.00863636363637 2014 75.86896551724138 2015 100.00909090909092 2016 81.4888888888889