Year	Annual Number
1970	0
1971	27
1972	0
1973	12
1974	14
1975	0
1976	0
1977	0
1978	7
1979	0
1980	0
1981	2
1982	0
1983	0
1984	36
1985	0
1986	8
1987	0
1988	16
1989	9
1990	12
1991	0
1992	0
1993	1
1994	0
1995	0
1996	5
1997	0
1998	20
1999	0
2000	0
2001	4
2002	0
2003	1
2004	3
2005	3
2006	0
2007	9
2008	5