| Year | Count |
|---|---|
| 1971 | 10 |
| 1972 | 39 |
| 1973 | 29 |
| 1974 | 48 |
| 1975 | 88 |
| 1976 | 41 |
| 1977 | 94 |
| 1978 | 93 |
| 1979 | 82 |
| 1980 | 72 |
| 1981 | 78 |
| 1982 | 82 |
| 1983 | 91 |
| 1984 | 90 |
| 1985 | 113 |
| 1986 | 96 |
| 1987 | 59 |
| 1988 | 102 |
| 1989 | 77 |
| 1990 | 114 |
| 1991 | 147 |
| 1992 | 176 |
| 1993 | 111 |
| 1994 | 63 |
| 1995 | 52 |
| 1996 | 41 |
| 1997 | 67 |
| 1998 | 66 |
| 1999 | 36 |
| 2000 | 26 |
| 2001 | 36 |
| 2002 | 5 |
| 2003 | 40 |
| 2004 | 11 |
| 2005 | 15 |
| 2006 | 20 |
| 2007 | 29 |
| 2008 | 6 |
| 2009 | 5 |
| 2010 | 5 |
| 2011 | 6 |