Year	Percent
1948	4
1949	4
1950	4
1951	5
1952	6
1953	4
1954	4
1955	5
1956	5
1957	5
1958	5
1959	5
1960	5
1961	5
1962	5
1963	5
1964	5
1965	5
1966	5
1967	4
1968	4
1969	5
1970	5
1971	5
1972	6
1973	6
1974	7
1975	6
1976	4
1977	6
1978	5
1979	4
1980	7
1981	7
1982	5
1983	4
1984	5
1985	4
1986	4
1987	3
1988	4
1989	7
1990	7
1991	8
1992	8
1993	5
1994	5
1995	3
1996	3
1997	3
1998	3