Year Percent 1948 6 1949 6 1950 6 1951 6 1952 6 1953 6 1954 6 1955 6 1956 6 1957 6 1958 6 1959 10 1960 10 1961 10 1962 10 1963 10 1964 10 1965 10 1966 10 1967 10 1968 10 1969 10 1970 10 1971 10 1972 10 1973 10 1974 10 1975 10 1976 13 1977 15 1978 29 1979 30 1980 30 1981 45 1982 45 1983 60 1984 60 1985 43 1986 36 1987 30 1988 748 1989 866 1990 290 1991 68 1992 48 1993 29 1994 16 1995 18 1996 18 1997 16 1998 19 1999 18 2000 14 2001 5 2002 5 2003 3 2004 4 2005 4 2006 5