Year	Percent
1948	2
1949	2
1950	2
1951	2
1952	2
1953	2
1954	2
1955	3
1956	4
1957	4
1958	4
1959	5
1960	4
1961	3
1962	4
1963	4
1964	4
1965	5
1966	5
1967	6
1968	7
1969	8
1970	6
1971	5
1972	5
1973	7
1974	9
1975	9
1976	9
1977	8
1978	11
1979	14
1980	17
1981	15
1982	10
1983	10
1984	10
1985	9
1986	8
1987	9
1988	11
1989	12
1990	12
1991	8
1992	7
1993	4
1994	7
1995	6
1996	3
1997	5
1998	5
1999	5
2000	6
2001	3
2002	3
2003	3
2004	3
2005	4
2006	5