Year	Percent
1980	25.07143
1981	23.37423
1982	20.65574
1983	25.31401
1984	15.80745
1985	18.0814
1986	18.52861
1987	23.43096
1988	23.95672
1989	19.94751
1990	20.26144
1997	7.62708
1998	6.75628
1999	6.19374
2000	6.62993
2001	6.7419
2002	5.18257
2003	9.40541
2004	11.39407
2005	13.76135
2006	14.5973