*Excludes Observations that spanned multiple years
| Pre 1970 | 117 |
|---|---|
| 1970 | 3 |
| 1971 | 7 |
| 1972 | 4 |
| 1973 | 2 |
| 1974 | 2 |
| 1975 | 2 |
| 1976 | 16 |
| 1977 | 9 |
| 1978 | 3 |
| 1979 | 5 |
| 1980 | 6 |
| 1981 | 10 |
| 1982 | 1 |
| 1983 | 13 |
| 1984 | 3 |
| 1985 | 5 |
| 1986 | 30 |
| 1987 | 5 |
| 1988 | 9 |
| 1989 | 18 |
| 1990 | 8 |
| 1991 | 59 |
| 1992 | 43 |
| 1993 | 37 |
| 1994 | 63 |
| 1995 | 82 |
| 1996 | 17 |
| 1997 | 39 |
| 1998 | 82 |
| 1999 | 47 |
| 2000 | 15 |
| 2001 | 271 |
| 2002 | 91 |
| 2003 | 99 |
| 2004 | 340 |
| 2005 | 102 |
| 2006 | 329 |
| 2007 | 837 |
| 2008 | 341 |
| 2009 | 439 |
| 2010 | 411 |
| 2011 | 585 |
| 2012 | 301 |
| 2013 | 178 |
| 2014 | 258 |
| 2015 | 532 |
| 2016 | 333 |
| 2017 | 637 |
| 2018 | 1069 |
| 2019 | 476 |
| 2020 | 882 |
| 2021 | 876 |
| 2022 | 1071 |
| 2023 | 1390 |
| 2024 | 1719 |
| 2025 | 3412 |
| 2026 | 31 |
| Total | 17772 |