Year	Percent
1948	4
1949	4
1950	6
1951	6
1952	6
1953	7
1954	7
1955	7
1956	7
1957	7
1958	7
1959	7
1960	10
1961	10
1962	10
1963	10
1964	11
1965	28
1966	28
1967	28
1968	23
1969	22
1970	19
1971	16
1972	11
1973	11
1974	11
1975	14
1976	14
1977	14
1978	15
1979	15
1980	16
1981	11
1982	5
1983	5
1984	5
1985	5
1986	7
1987	7
1988	8
1989	7
1990	7
1991	7
1992	7
1993	5
1994	5
1995	5
1996	5
1997	5
1998	3
1999	3
2000	3
2001	3
2002	3
2003	3
2004	2
2005	2
2006	3