| Year | Count |
|---|---|
| 1970 | 5 |
| 1971 | 7 |
| 1972 | 17 |
| 1973 | 41 |
| 1974 | 16 |
| 1975 | 64 |
| 1976 | 103 |
| 1977 | 96 |
| 1978 | 117 |
| 1979 | 172 |
| 1980 | 256 |
| 1981 | 244 |
| 1982 | 243 |
| 1983 | 367 |
| 1984 | 331 |
| 1985 | 453 |
| 1986 | 473 |
| 1987 | 461 |
| 1988 | 554 |
| 1989 | 647 |
| 1990 | 542 |
| 1991 | 516 |
| 1992 | 585 |
| 1993 | 647 |
| 1994 | 547 |
| 1995 | 504 |
| 1996 | 487 |
| 1997 | 494 |
| 1998 | 574 |
| 1999 | 609 |
| 2000 | 533 |
| 2001 | 404 |
| 2002 | 241 |
| 2003 | 124 |
| 2004 | 120 |
| 2005 | 84 |
| 2006 | 84 |
| 2007 | 35 |
| 2008 | 39 |
| 2009 | 6 |
| 2010 | 24 |
| 2012 | 32 |
| 2013 | 10 |
| 2014 | 22 |
| 2015 | 10 |
| 2016 | 16 |
| 2017 | 10 |
| 2018 | 8 |
| 2019 | 5 |