Year	Percent
1984	10
1985	7
1986	12
1987	16
1988	17
1989	32
1990	32
1991	28
1992	25
1993	19
1994	24
1995	26
1996	22
1997	30
1998	20
1999	30
2000	28
2001	26
2002	25
2003	23
2004	16
2005	27
2006	39
2007	31
2008	27
2009	36
2010	33
2011	28