| Year | Count |
|---|---|
| 1961 | 15 |
| 1963 | 10 |
| 1966 | 14 |
| 1967 | 16 |
| 1968 | 5 |
| 1969 | 18 |
| 1970 | 151 |
| 1971 | 354 |
| 1972 | 454 |
| 1973 | 463 |
| 1974 | 453 |
| 1975 | 444 |
| 1976 | 413 |
| 1977 | 432 |
| 1978 | 417 |
| 1979 | 397 |
| 1980 | 340 |
| 1981 | 292 |
| 1982 | 402 |
| 1983 | 432 |
| 1984 | 433 |
| 1985 | 449 |
| 1986 | 282 |
| 1987 | 247 |
| 1988 | 269 |
| 1989 | 171 |
| 1990 | 198 |
| 1991 | 144 |
| 1992 | 50 |
| 1993 | 112 |
| 1994 | 72 |
| 1995 | 63 |
| 1996 | 5 |
| 1997 | 52 |
| 1998 | 47 |
| 1999 | 15 |
| 2000 | 10 |
| 2001 | 21 |
| 2002 | 19 |
| 2005 | 29 |
| 2006 | 6 |
| 2007 | 15 |
| 2008 | 9 |