*Excludes Observations that spanned multiple years
| Pre 1970 | 93 |
|---|---|
| 1970 | 0 |
| 1971 | 4 |
| 1972 | 0 |
| 1973 | 0 |
| 1974 | 0 |
| 1975 | 1 |
| 1976 | 1 |
| 1977 | 2 |
| 1978 | 0 |
| 1979 | 3 |
| 1980 | 1 |
| 1981 | 0 |
| 1982 | 2 |
| 1983 | 0 |
| 1984 | 2 |
| 1985 | 66 |
| 1986 | 105 |
| 1987 | 128 |
| 1988 | 386 |
| 1989 | 42 |
| 1990 | 26 |
| 1991 | 196 |
| 1992 | 72 |
| 1993 | 205 |
| 1994 | 107 |
| 1995 | 261 |
| 1996 | 121 |
| 1997 | 131 |
| 1998 | 22 |
| 1999 | 103 |
| 2000 | 100 |
| 2001 | 73 |
| 2002 | 36 |
| 2003 | 78 |
| 2004 | 70 |
| 2005 | 72 |
| 2006 | 61 |
| 2007 | 75 |
| 2008 | 87 |
| 2009 | 71 |
| 2010 | 79 |
| 2011 | 61 |
| 2012 | 88 |
| 2013 | 83 |
| 2014 | 73 |
| 2015 | 78 |
| 2016 | 96 |
| 2017 | 82 |
| 2018 | 64 |
| 2019 | 81 |
| 2020 | 60 |
| 2021 | 126 |
| 2022 | 68 |
| 2023 | 54 |
| 2024 | 130 |
| 2025 | 17 |
| 2026 | 1 |
| Total | 4044 |