| Year | Count |
|---|---|
| 1977 | 9 |
| 1978 | 8 |
| 1979 | 34 |
| 1980 | 79 |
| 1981 | 155 |
| 1982 | 183 |
| 1983 | 447 |
| 1984 | 642 |
| 1985 | 1,350 |
| 1986 | 1,623 |
| 1987 | 2,247 |
| 1988 | 3,252 |
| 1989 | 3,899 |
| 1990 | 3,897 |
| 1990 | 6 |
| 1991 | 4,535 |
| 1992 | 3,440 |
| 1993 | 3,797 |
| 1994 | 4,205 |
| 1995 | 4,236 |
| 1996 | 3,738 |
| 1997 | 3,205 |
| 1998 | 3,531 |
| 1999 | 2,293 |
| 2000 | 2,373 |
| 2001 | 1,983 |
| 2002 | 1,540 |
| 2003 | 1,249 |
| 2004 | 1,378 |
| 2005 | 1,251 |
| 2006 | 1,131 |
| 2007 | 955 |
| 2008 | 740 |
| 2009 | 529 |
| 2010 | 417 |
| 2011 | 341 |
| 2012 | 246 |
| 2013 | 181 |
| 2014 | 169 |
| 2015 | 168 |
| 2016 | 45 |
| 2017 | 32 |
| 2018 | 5 |
| 2019 | 25 |