| Year | Count |
|---|---|
| 1970 | 6 |
| 1971 | 7 |
| 1972 | 11 |
| 1973 | 37 |
| 1974 | 111 |
| 1975 | 127 |
| 1976 | 228 |
| 1977 | 444 |
| 1978 | 454 |
| 1979 | 382 |
| 1980 | 458 |
| 1981 | 324 |
| 1982 | 268 |
| 1983 | 296 |
| 1984 | 396 |
| 1985 | 312 |
| 1986 | 250 |
| 1987 | 148 |
| 1988 | 148 |
| 1989 | 114 |
| 1990 | 90 |
| 1991 | 74 |
| 1992 | 62 |
| 1993 | 37 |
| 1994 | 17 |
| 1995 | 21 |
| 1996 | 18 |
| 1997 | 11 |
| 1998 | 6 |
| 1999 | 6 |
| 2000 | 7 |
| 2002 | 5 |
| 2003 | 6 |
| 2004 | 7 |
| 2006 | 6 |