Year	Percent
1971	3.528
1972	3.485
1973	7.744
1974	12.98
1975	21.15
1976	9.831
1977	2.137
1978	23.11
1979	13.34
1980	7.048
1981	15.09
1982	9.563
1983	5.075
1984	9.128
1985	11.22
1986	19.07
1987	12.41
1988	4.72
1989	5.812
1990	4.906
1991	3.611
1992	7.596
1993	1.538
1994	8.117
1995	6.824
1996	4.395
1997	7.956
1998	6.503
1999	8.633
2000	4.378
2001	14.78
2002	8.179
2003	10.77
2004	7.535
2005	11.5
2006	12.29
2007	7.281