Year	Percent
1971	2.743
1972	1.607
1973	1.867
1974	3.683
1979	1.987
1980	2.273
1981	3.141
1982	2.844
1983	2.383
1984	18.87
1985	7.248
1986	3.75
1987	3.588
1988	8.714
1989	7.709
1990	7.661
1991	3.308
1992	7.828
1993	12.93
1994	12.06
1995	11.52
1996	12.93
1997	12.45
1998	12.79
1999	8.4
2000	19.46
2001	7.539
2002	5.214
2003	14.08
2004	8.46
2005	22.76
2006	15.45
2007	21.77