Year	Percent
1976	8
1977	8
1978	7
1979	6
1980	6
1981	9
1982	12
1983	11
1984	9
1985	9
1986	9
1987	9
1988	7
1989	7
1990	9
1991	12
1992	14
1993	14
1994	14
1995	13
1996	13
1997	12
1998	13
1999	14
2000	14
2001	14
2002	15
2003	14
2004	14
2005	15
2006	15