Year	Percent
1948	3
1949	3
1950	5
1951	5
1952	5
1953	4
1954	5
1955	6
1956	6
1957	6
1958	5
1959	5
1960	6
1961	7
1962	7
1963	6
1964	7
1965	7
1966	7
1967	8
1968	6
1969	9
1970	9
1971	8
1972	7
1973	9
1974	10
1975	8
1976	10
1977	9
1978	8
1979	11
1980	11
1981	11
1982	10
1983	7
1984	7
1985	7
1986	7
1987	7
1988	7
1989	7
1990	9
1991	10
1992	10
1993	6
1994	5
1995	4
1996	3
1997	4
1998	4
1999	3
2000	5
2001	3
2002	3
2003	2
2004	2
2005	2
2006	4