Year	Percent
1966	6
1967	5
1968	5
1969	5
1970	5
1971	5
1972	5
1973	5
1974	5
1975	5
1976	6
1977	6
1978	6
1979	6
1980	6
1981	7
1982	7
1983	6
1984	6
1985	6
1986	6
1987	6
1988	6
1989	8
1990	9
1991	9
1992	9
1993	9
1994	9
1995	9
1996	9
1997	8
1998	9
1999	8
2000	7
2001	5
2002	5
2003	3
2004	4
2005	7
2006	8