Year	Annual Number
1970	28
1971	0
1972	747
1973	0
1974	0
1975	0
1976	0
1977	315
1978	27
1979	0
1980	0
1981	0
1982	0
1983	0
1984	166
1985	0
1986	0
1987	50
1988	0
1989	0
1990	127
1991	54
1992	5
1993	0
1994	0
1995	0
1996	85
1997	15
1998	403
1999	64
2000	20
2001	70
2002	21
2003	0
2004	10
2005	18
2006	46
2007	3
2008	10