| Year | Count |
|---|---|
| 1971 | 5 |
| 1975 | 9 |
| 1976 | 6 |
| 1977 | 28 |
| 1978 | 30 |
| 1979 | 32 |
| 1980 | 49 |
| 1981 | 55 |
| 1982 | 49 |
| 1983 | 46 |
| 1984 | 48 |
| 1985 | 62 |
| 1986 | 94 |
| 1987 | 82 |
| 1988 | 69 |
| 1989 | 95 |
| 1990 | 148 |
| 1991 | 148 |
| 1992 | 167 |
| 1993 | 186 |
| 1994 | 200 |
| 1995 | 261 |
| 1996 | 265 |
| 1997 | 361 |
| 1998 | 427 |
| 1999 | 439 |
| 2000 | 516 |
| 2001 | 559 |
| 2002 | 474 |
| 2003 | 533 |
| 2004 | 532 |
| 2005 | 590 |
| 2006 | 642 |
| 2007 | 582 |
| 2008 | 616 |
| 2009 | 714 |
| 2010 | 609 |
| 2011 | 687 |
| 2012 | 670 |
| 2013 | 653 |
| 2014 | 759 |
| 2015 | 748 |
| 2016 | 843 |
| 2017 | 866 |
| 2018 | 820 |
| 2019 | 710 |
| 2020 | 507 |
| 2021 | 550 |
| 2022 | 512 |
| 2023 | 528 |
| 2024 | 523 |