Year	Percent
1980	8
1981	10
1982	11
1983	16
1984	24
1985	24
1986	36
1987	31
1988	45
1989	55
1990	50
1991	46
1992	41
1993	24
1994	15
1995	13
1996	16
1997	14
1998	9
1999	16
2000	19
2001	9
2002	13
2003	26
2004	16
2005	14
2006	16