| Year | Count |
|---|---|
| 1968 | 5 |
| 1970 | 7 |
| 1971 | 7 |
| 1973 | 5 |
| 1974 | 6 |
| 1975 | 9 |
| 1976 | 5 |
| 1977 | 8 |
| 1978 | 5 |
| 1979 | 8 |
| 1980 | 9 |
| 1981 | 8 |
| 1982 | 8 |
| 1983 | 5 |
| 1984 | 8 |
| 1985 | 12 |
| 1986 | 8 |
| 1987 | 8 |
| 1988 | 7 |
| 1989 | 13 |
| 1990 | 12 |
| 1991 | 10 |
| 1992 | 14 |
| 1993 | 12 |
| 1994 | 15 |
| 1995 | 23 |
| 1997 | 7 |
| 1998 | 8 |
| 1999 | 9 |
| 2002 | 10 |
| 2003 | 7 |
| 2004 | 10 |
| 2005 | 8 |
| 2007 | 7 |
| 2010 | 6 |