Year	Annual Number
1970	0
1971	115
1972	0
1973	1
1974	1
1975	0
1976	38
1977	1
1978	11
1979	13
1980	2
1981	0
1982	5
1983	22
1984	0
1985	2
1986	5
1987	0
1988	0
1989	9
1990	0
1991	22
1992	2
1993	7
1994	0
1995	0
1996	0
1997	1
1998	0
1999	2
2000	0
2001	0
2002	0
2003	4
2004	0
2005	0
2006	0
2007	0
2008	2