Year Percent 1948 4 1949 4 1950 4 1951 4 1952 4 1953 4 1954 4 1955 4 1956 4 1957 4 1958 4 1959 4 1960 6 1961 6 1962 6 1963 4 1964 4 1965 4 1966 5 1967 5 1968 7 1969 8 1970 8 1971 7 1972 8 1973 9 1974 9 1975 8 1976 8 1977 8 1978 10 1979 9 2003 12