| Year | Count |
|---|---|
| 1987 | 12 |
| 1988 | 12 |
| 1990 | 46 |
| 1991 | 37 |
| 1992 | 62 |
| 1993 | 48 |
| 1994 | 122 |
| 1995 | 201 |
| 1996 | 256 |
| 1997 | 251 |
| 1998 | 233 |
| 1999 | 375 |
| 2000 | 495 |
| 2001 | 498 |
| 2002 | 278 |
| 2003 | 324 |
| 2004 | 283 |
| 2005 | 233 |
| 2006 | 172 |
| 2007 | 101 |
| 2008 | 133 |
| 2009 | 68 |
| 2010 | 30 |
| 2011 | 26 |
| 2012 | 18 |
| 2013 | 15 |
| 2014 | 23 |
| 2015 | 10 |
| 2016 | 6 |
| 2017 | 6 |