Year	Percent
1948	12
1949	12
1950	12
1951	12
1952	12
1953	12
1954	10
1955	9
1956	11
1957	11
1958	11
1959	9
1960	6
1961	6
1962	6
1963	6
1964	6
1965	6
1966	6
1967	5
1968	5
1969	7
1970	7
1971	7
1972	7
1973	9
1974	8
1975	10
1976	10
1977	11
1978	14
1979	19
1980	21
1981	21
1982	21
1983	21
1984	21
1985	21
1986	21
1987	21
1988	19
1989	19
1990	19
1991	19
1992	19
1993	22
1994	21
1995	18
1996	17
1997	15
1999	12
2000	8