Year	Percent
1976	9
1977	9
1978	9
1979	7
1980	7
1981	11
1982	16
1983	14
1984	19
1985	13
1986	10
1987	9
1988	11
1989	12
1990	12
1991	13
1992	12
1993	11
1994	12
1995	15
1996	17
1997	16
1998	18
1999	12
2000	11
2001	10
2002	14
2003	8
2004	8
2005	7
2006	9