*Excludes Observations that spanned multiple years
| Pre 1970 | 52 |
|---|---|
| 1970 | 0 |
| 1971 | 1 |
| 1972 | 0 |
| 1973 | 1 |
| 1974 | 0 |
| 1975 | 1 |
| 1976 | 1 |
| 1977 | 0 |
| 1978 | 0 |
| 1979 | 2 |
| 1980 | 1 |
| 1981 | 0 |
| 1982 | 1 |
| 1983 | 1 |
| 1984 | 0 |
| 1985 | 0 |
| 1986 | 32 |
| 1987 | 22 |
| 1988 | 49 |
| 1989 | 18 |
| 1990 | 9 |
| 1991 | 28 |
| 1992 | 11 |
| 1993 | 16 |
| 1994 | 15 |
| 1995 | 20 |
| 1996 | 13 |
| 1997 | 27 |
| 1998 | 5 |
| 1999 | 36 |
| 2000 | 222 |
| 2001 | 363 |
| 2002 | 261 |
| 2003 | 163 |
| 2004 | 82 |
| 2005 | 74 |
| 2006 | 153 |
| 2007 | 74 |
| 2008 | 280 |
| 2009 | 1961 |
| 2010 | 120 |
| 2011 | 236 |
| 2012 | 173 |
| 2013 | 128 |
| 2014 | 201 |
| 2015 | 340 |
| 2016 | 222 |
| 2017 | 225 |
| 2018 | 427 |
| 2019 | 237 |
| 2020 | 490 |
| 2021 | 697 |
| 2022 | 2818 |
| 2023 | 1284 |
| 2024 | 636 |
| 2025 | 981 |
| 2026 | 33 |
| Total | 13243 |