Year	Percent
1966	6
1967	7
1968	7
1969	7
1970	7
1971	7
1972	7
1973	7
1974	7
1975	7
1976	7
1977	7
1978	9
1979	11
1980	13
1981	13
1982	14
1983	14
1984	14
1985	14
1986	14
1987	14
1988	14
1989	35
1990	30
1991	33
1992	24
1993	17
1994	20
1995	17
1996	12
1997	11
1998	11
1999	13
2000	12
2001	9
2002	6
2003	6
2004	6
2005	6
2006	7