Year	Percent
1980	17.71
1985	24.37
1986	10.3
1988	7.09
1989	6.83
1990	9.8
1991	6.58
1992	7.19
1993	6.84
1994	6.43
1995	5.88
1996	6.48
1997	5.32
1998	5.78
1999	4.45
2000	3.74
2001	5.22
2002	3.22
2003	3.2
2004	3.42
2006	3.9
2007	3.73