Year	Percent
1964	5
1965	5
1966	5
1967	5
1968	5
1969	5
1970	5
1971	5
1972	5
1973	5
1974	5
1975	5
1976	5
1977	5
1978	5
1979	9
1980	9
1981	9
1982	9
1983	9
1984	9
1985	9
1986	9
1987	9
1988	9
1989	9
1990	14
1991	14
1992	11
1993	11
1994	11
1995	16
1996	16
1997	11
1998	11
1999	11
2000	12
2001	13
2002	13
2003	15
2004	15
2005	13