| Year | Count |
|---|---|
| 1971 | 6 |
| 1972 | 12 |
| 1973 | 21 |
| 1974 | 38 |
| 1975 | 29 |
| 1976 | 56 |
| 1977 | 176 |
| 1978 | 95 |
| 1979 | 148 |
| 1980 | 141 |
| 1981 | 152 |
| 1982 | 122 |
| 1983 | 108 |
| 1984 | 165 |
| 1985 | 194 |
| 1986 | 169 |
| 1987 | 229 |
| 1988 | 128 |
| 1989 | 155 |
| 1990 | 342 |
| 1991 | 3,049 |
| 1992 | 706 |
| 1993 | 478 |
| 1994 | 415 |
| 1995 | 316 |
| 1996 | 316 |
| 1997 | 157 |
| 1998 | 70 |
| 1999 | 62 |
| 2000 | 49 |
| 2001 | 42 |
| 2002 | 6 |
| 2003 | 14 |
| 2004 | 30 |
| 2005 | 16 |
| 2006 | 15 |
| 2008 | 10 |