Year	Percent
1948	3
1949	3
1950	3
1951	3
1952	3
1953	3
1954	3
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	5
1970	5
1971	5
1972	5
1973	5
1974	6
1975	5
1976	6
1977	6
1978	7
1979	9
1980	9
1981	9
1982	9
1983	10
1984	10
1985	11
1986	15
1987	14
1988	12
1989	11
1990	11
1991	10
1992	11
1993	7
1994	7
1995	7
1996	6
1997	6
1998	10
1999	8
2000	9
2001	9
2002	9
2003	4
2004	4
2005	4
2006	6