Year Annual Number 1970 35 1971 0 1972 0 1973 38 1974 0 1975 0 1976 0 1977 0 1978 1 1979 0 1980 0 1981 0 1982 0 1983 0 1984 0 1985 0 1986 0 1987 33 1988 0 1989 0 1990 6 1991 0 1992 0 1993 8 1994 3 1995 0 1996 0 1997 22 1998 0 1999 0 2000 0 2001 0 2002 0 2003 0 2004 0 2005 0 2006 1 2007 0 2008 0