| Year | Count |
|---|---|
| 1971 | 10 |
| 1972 | 18 |
| 1974 | 21 |
| 1975 | 17 |
| 1976 | 16 |
| 1977 | 21 |
| 1979 | 23 |
| 1980 | 15 |
| 1981 | 24 |
| 1982 | 18 |
| 1984 | 6 |
| 1985 | 34 |
| 1986 | 15 |
| 1987 | 5 |
| 1988 | 10 |
| 1989 | 5 |
| 1990 | 13 |
| 1991 | 13 |
| 1993 | 10 |
| 1998 | 5 |
| 2001 | 10 |
| 2002 | 10 |
| 2003 | 65 |
| 2004 | 88 |
| 2005 | 42 |
| 2006 | 31 |
| 2007 | 25 |
| 2008 | 36 |
| 2009 | 38 |
| 2010 | 12 |
| 2011 | 5 |