| Year | Count |
|---|---|
| 1961 | 11 |
| 1964 | 21 |
| 1965 | 10 |
| 1966 | 23 |
| 1967 | 44 |
| 1968 | 87 |
| 1969 | 95 |
| 1970 | 83 |
| 1971 | 100 |
| 1972 | 55 |
| 1973 | 72 |
| 1974 | 86 |
| 1975 | 92 |
| 1976 | 59 |
| 1977 | 111 |
| 1978 | 72 |
| 1979 | 106 |
| 1980 | 90 |
| 1981 | 76 |
| 1982 | 83 |
| 1983 | 77 |
| 1984 | 87 |
| 1985 | 102 |
| 1986 | 89 |
| 1987 | 181 |
| 1988 | 229 |
| 1989 | 366 |
| 1990 | 408 |
| 1991 | 456 |
| 1992 | 429 |
| 1993 | 300 |
| 1994 | 245 |
| 1995 | 273 |
| 1996 | 315 |
| 1997 | 237 |
| 1998 | 218 |
| 1999 | 220 |
| 2000 | 215 |
| 2001 | 145 |
| 2002 | 116 |
| 2003 | 130 |
| 2004 | 108 |
| 2005 | 97 |
| 2006 | 84 |
| 2007 | 49 |
| 2008 | 24 |
| 2009 | 10 |
| 2010 | 5 |