Year	Percent
1974	3
1975	3
1976	3
1977	3
1978	3
1979	3
1980	3
1981	3
1982	3
1983	3
1984	3
1985	3
1986	5
1987	5
1988	5
1989	7
1990	11
1991	12
1992	12
1993	12
1994	21
1995	14
1996	13
1997	11
1998	10
1999	9
2000	6
2001	6
2002	6
2003	5
2004	4
2005	4
2006	4