Year	Annual Number
1970	0
1971	17
1972	0
1973	0
1974	13
1975	29
1976	720
1977	10
1978	0
1979	0
1980	0
1981	100
1982	225
1983	275
1984	4
1985	0
1986	0
1987	0
1988	288
1989	0
1990	38
1991	13
1992	3
1993	38
1994	0
1995	170
1996	16
1997	242
1998	255
1999	9
2000	31
2001	5
2002	16
2003	4
2004	20
2005	47
2006	15
2007	20
2008	2