Year	Percent
1960	6
1961	6
1962	5
1963	4
1964	5
1965	5
1966	5
1967	5
1968	5
1969	5
1970	5
1971	5
1972	5
1973	5
1974	5
1975	4
1976	4
1977	4
1978	5
1979	5
1980	6
1981	6
1982	8
1983	8
1984	10
1985	10
1986	10
1987	13
1988	13
1989	19
1990	19
1991	16
1992	18
1993	26
1994	14
1995	14
1996	14
1997	14
1998	14
1999	18
2000	14
2001	21
2002	17
2003	15
2004	15
2005	13
2006	10