| Year | Count |
|---|---|
| 1960 | 6 |
| 1965 | 16 |
| 1966 | 16 |
| 1967 | 12 |
| 1968 | 62 |
| 1969 | 71 |
| 1970 | 53 |
| 1971 | 79 |
| 1972 | 49 |
| 1973 | 44 |
| 1974 | 52 |
| 1975 | 43 |
| 1976 | 50 |
| 1977 | 69 |
| 1978 | 102 |
| 1979 | 97 |
| 1980 | 199 |
| 1981 | 273 |
| 1982 | 239 |
| 1983 | 215 |
| 1984 | 240 |
| 1985 | 329 |
| 1986 | 337 |
| 1987 | 303 |
| 1988 | 433 |
| 1989 | 450 |
| 1990 | 450 |
| 1991 | 407 |
| 1992 | 372 |
| 1993 | 275 |
| 1994 | 265 |
| 1995 | 224 |
| 1996 | 233 |
| 1997 | 160 |
| 1998 | 135 |
| 1999 | 74 |
| 2000 | 80 |
| 2001 | 84 |
| 2002 | 56 |
| 2003 | 19 |
| 2004 | 59 |
| 2005 | 30 |
| 2006 | 12 |
| 2007 | 16 |
| 2008 | 14 |
| 2009 | 15 |
| 2010 | 5 |
| 2012 | 15 |