| Year | Count |
|---|---|
| 1956 | 6 |
| 1960 | 10 |
| 1961 | 20 |
| 1963 | 9 |
| 1964 | 16 |
| 1965 | 19 |
| 1966 | 16 |
| 1967 | 17 |
| 1968 | 20 |
| 1969 | 30 |
| 1970 | 33 |
| 1971 | 27 |
| 1972 | 37 |
| 1973 | 31 |
| 1974 | 38 |
| 1975 | 53 |
| 1976 | 33 |
| 1977 | 112 |
| 1978 | 96 |
| 1979 | 84 |
| 1980 | 82 |
| 1981 | 41 |
| 1982 | 54 |
| 1983 | 50 |
| 1984 | 52 |
| 1985 | 47 |
| 1986 | 51 |
| 1987 | 41 |
| 1988 | 49 |
| 1989 | 43 |
| 1990 | 48 |
| 1991 | 40 |
| 1992 | 55 |
| 1993 | 33 |
| 1994 | 56 |
| 1995 | 20 |
| 1996 | 50 |
| 1997 | 17 |
| 1998 | 26 |
| 1999 | 19 |
| 2000 | 14 |
| 2001 | 17 |
| 2002 | 14 |
| 2003 | 18 |
| 2004 | 8 |
| 2005 | 12 |
| 2006 | 6 |
| 2007 | 9 |
| 2008 | 9 |
| 2010 | 7 |
| 2011 | 6 |