Year	Percent
1950	3
1951	3
1952	3
1953	3
1954	3
1955	3
1956	3
1957	3
1958	3
1959	3
1960	4
1961	4
1962	4
1963	4
1964	4
1965	5
1966	5
1967	5
1968	6
1969	6
1970	7
1971	7
1972	7
1973	7
1974	7
1975	7
1976	7
1977	10
1978	10
1979	10
1980	12
1981	14
1982	14
1983	13
1984	13
1985	11
1986	11
1987	10
1988	10
1989	14
1990	15
1991	17
1992	17
1993	17
1994	17
1995	17
1996	17
1997	17
1998	17
1999	16
2000	25
2002	18
2003	15
2004	15
2005	15