Year	Percent
1963	5
1964	5
1965	5
1966	5
1967	5
1968	6
1969	6
1970	6
1971	6
1972	6
1973	6
1974	6
1975	6
1976	7
1977	7
1978	7
1979	8
1980	10
1981	10
1982	10
1983	10
1984	10
1985	11
1986	11
1987	14
1988	11
1989	11
1990	14
1991	13
1992	20
1993	25
1994	40
1995	50
1996	27
1997	23
1998	43
1999	47
2000	50
2001	47
2002	40
2003	35
2004	25
2005	25
2006	20