| Year | Count |
|---|---|
| 1960 | 5 |
| 1966 | 5 |
| 1967 | 21 |
| 1968 | 18 |
| 1969 | 37 |
| 1970 | 57 |
| 1971 | 19 |
| 1972 | 45 |
| 1973 | 44 |
| 1974 | 30 |
| 1975 | 25 |
| 1976 | 15 |
| 1977 | 25 |
| 1978 | 67 |
| 1979 | 28 |
| 1980 | 42 |
| 1981 | 47 |
| 1982 | 80 |
| 1983 | 52 |
| 1984 | 76 |
| 1985 | 99 |
| 1986 | 100 |
| 1987 | 132 |
| 1988 | 123 |
| 1989 | 564 |
| 1990 | 108 |
| 1991 | 80 |
| 1992 | 100 |
| 1993 | 79 |
| 1994 | 23 |
| 1995 | 45 |
| 1996 | 23 |
| 1997 | 20 |
| 1998 | 20 |
| 2001 | 27 |
| 2004 | 22 |
| 2006 | 14 |
| 2008 | 9 |
| 2009 | 5 |
| 2010 | 5 |