| Year | Count |
|---|---|
| 1968 | 5 |
| 1973 | 9 |
| 1974 | 11 |
| 1975 | 10 |
| 1976 | 22 |
| 1977 | 48 |
| 1978 | 54 |
| 1979 | 54 |
| 1980 | 76 |
| 1981 | 37 |
| 1982 | 37 |
| 1983 | 58 |
| 1984 | 91 |
| 1985 | 120 |
| 1986 | 98 |
| 1987 | 97 |
| 1988 | 96 |
| 1989 | 150 |
| 1990 | 141 |
| 1991 | 123 |
| 1992 | 112 |
| 1993 | 96 |
| 1994 | 93 |
| 1995 | 77 |
| 1996 | 74 |
| 1997 | 75 |
| 1998 | 56 |
| 1999 | 52 |
| 2000 | 55 |
| 2001 | 22 |
| 2002 | 36 |
| 2003 | 32 |
| 2004 | 29 |
| 2005 | 21 |
| 2006 | 23 |
| 2007 | 24 |
| 2008 | 19 |
| 2009 | 8 |
| 2010 | 13 |
| 2011 | 9 |
| 2012 | 6 |
| 2013 | 9 |
| 2014 | 11 |
| 2015 | 15 |
| 2016 | 18 |