Year	Percent
1974	6
1975	6
1976	6
1977	6
1978	6
1979	6
1980	8
1981	10
1982	10
1983	10
1984	10
1985	15
1986	20
1987	21
1988	19
1989	15
1990	17
1991	16
1992	18
1993	14
1994	14
1995	14
1996	14
1997	14
1998	12
1999	11
2000	10
2001	13
2002	18
2003	29
2004	28
2005	14
2006	9