| Year | Count |
|---|---|
| 1961 | 6 |
| 1963 | 5 |
| 1965 | 5 |
| 1969 | 7 |
| 1970 | 13 |
| 1971 | 16 |
| 1972 | 48 |
| 1973 | 83 |
| 1974 | 75 |
| 1975 | 124 |
| 1976 | 108 |
| 1977 | 278 |
| 1978 | 292 |
| 1979 | 284 |
| 1980 | 204 |
| 1981 | 129 |
| 1982 | 125 |
| 1983 | 103 |
| 1984 | 94 |
| 1985 | 93 |
| 1986 | 64 |
| 1987 | 66 |
| 1988 | 59 |
| 1989 | 60 |
| 1990 | 73 |
| 1991 | 52 |
| 1992 | 37 |
| 1993 | 49 |
| 1994 | 36 |
| 1995 | 46 |
| 1996 | 60 |
| 1997 | 34 |
| 1998 | 35 |
| 1999 | 39 |
| 2000 | 28 |
| 2001 | 18 |
| 2001 | 6 |
| 2002 | 22 |
| 2003 | 14 |
| 2004 | 12 |
| 2004 | 5 |
| 2005 | 17 |
| 2006 | 10 |
| 2007 | 5 |
| 2008 | 5 |
| 2008 | 5 |
| 2009 | 8 |
| 2011 | 6 |
| 2012 | 5 |