Year	Percent
1948	4
1949	4
1950	4
1951	4
1952	4
1953	4
1954	4
1955	4
1956	4
1957	4
1958	5
1959	5
1960	5
1961	5
1962	5
1963	8
1964	8
1965	8
1966	8
1967	8
1968	8
1969	8
1970	14
1971	14
1972	14
1973	14
1974	16
1975	16
1976	20
1977	20
1978	22
1979	30
1980	30
1981	30
1982	27
1983	27
1984	27
1985	27
1986	34
1987	35
1988	34
1989	37
1990	46
1991	45
1992	34
1993	33
1994	45
1995	40
1996	35
1997	31
1998	42
1999	23
2000	18
2001	13
2002	10
2003	12
2004	11
2005	11
2006	11