| Year | Count |
|---|---|
| 1970 | 12 |
| 1971 | 14 |
| 1974 | 5 |
| 1977 | 15 |
| 1978 | 7 |
| 1979 | 36 |
| 1980 | 12 |
| 1981 | 57 |
| 1982 | 70 |
| 1983 | 102 |
| 1984 | 90 |
| 1985 | 196 |
| 1986 | 260 |
| 1987 | 276 |
| 1988 | 306 |
| 1989 | 240 |
| 1990 | 266 |
| 1991 | 180 |
| 1992 | 300 |
| 1993 | 412 |
| 1994 | 242 |
| 1995 | 198 |
| 1996 | 160 |
| 1997 | 174 |
| 1998 | 160 |
| 1999 | 113 |
| 2000 | 68 |
| 2001 | 96 |
| 2002 | 48 |
| 2003 | 74 |
| 2004 | 87 |
| 2005 | 80 |
| 2006 | 28 |
| 2007 | 32 |
| 2008 | 47 |
| 2010 | 23 |
| 2011 | 7 |
| 2012 | 14 |