| Year | Count |
|---|---|
| 1970 | 8 |
| 1971 | 8 |
| 1972 | 12 |
| 1973 | 12 |
| 1974 | 10 |
| 1975 | 12 |
| 1976 | 15 |
| 1977 | 17 |
| 1978 | 22 |
| 1979 | 20 |
| 1980 | 25 |
| 1981 | 6 |
| 1982 | 21 |
| 1983 | 8 |
| 1984 | 17 |
| 1986 | 5 |
| 1988 | 5 |
| 1992 | 6 |
| 1994 | 5 |
| 1995 | 6 |
| 1996 | 10 |
| 1998 | 7 |
| 1999 | 9 |
| 2003 | 12 |
| 2005 | 13 |
| 2006 | 7 |
| 2007 | 11 |
| 2008 | 20 |
| 2009 | 28 |
| 2011 | 5 |
| 2012 | 15 |
| 2015 | 22 |
| 2016 | 10 |
| 2018 | 5 |
| 2019 | 5 |
| 2020 | 5 |
| 2021 | 6 |
| 2022 | 12 |