Year	Percent
1960	4
1961	5
1962	5
1963	5
1964	5
1965	5
1966	7
1967	6
1968	6
1969	6
1970	6
1971	8
1972	8
1973	6
1974	6
1975	8
1976	8
1977	8
1978	14
1979	14
1980	14
1981	20
1982	11
1983	15
1984	18
1985	19
1986	21
1987	24
1988	26
1989	26
1990	33
1991	20
1992	30
1993	35
1994	33
1995	45
1996	45
1997	45
1998	37
1999	27
2000	27
2001	27
2002	25
2003	22
2004	19
2005	16
2006	13