Year	Percent
1948	6
1949	5
1950	4
1951	4
1952	4
1953	4
1954	4
1955	4
1956	4
1957	4
1958	4
1959	4
1960	4
1961	4
1962	4
1963	4
1964	4
1965	4
1966	4
1967	4
1968	4
1969	4
1970	6
1971	5
1972	4
1973	7
1974	8
1975	6
1976	15
1977	12
1978	11
1979	15
1980	17
1981	19
1982	18
1983	17
1984	17
1985	15
1986	12
1987	12
1988	13
1989	14
1990	13
1991	12
1992	12
1993	8
1994	8
1995	9
1996	8
1997	6
1998	3