*Excludes Observations that spanned multiple years
| Pre 1970 | 127 |
|---|---|
| 1970 | 1 |
| 1971 | 1 |
| 1972 | 1 |
| 1973 | 1 |
| 1974 | 7 |
| 1975 | 5 |
| 1976 | 10 |
| 1977 | 2 |
| 1978 | 0 |
| 1979 | 8 |
| 1980 | 5 |
| 1981 | 9 |
| 1982 | 1 |
| 1983 | 6 |
| 1984 | 0 |
| 1985 | 1 |
| 1986 | 22 |
| 1987 | 17 |
| 1988 | 276 |
| 1989 | 19 |
| 1990 | 9 |
| 1991 | 35 |
| 1992 | 80 |
| 1993 | 86 |
| 1994 | 161 |
| 1995 | 133 |
| 1996 | 56 |
| 1997 | 97 |
| 1998 | 6 |
| 1999 | 3 |
| 2000 | 4 |
| 2001 | 24 |
| 2002 | 55 |
| 2003 | 82 |
| 2004 | 92 |
| 2005 | 84 |
| 2006 | 83 |
| 2007 | 88 |
| 2008 | 96 |
| 2009 | 81 |
| 2010 | 168 |
| 2011 | 160 |
| 2012 | 95 |
| 2013 | 115 |
| 2014 | 116 |
| 2015 | 104 |
| 2016 | 143 |
| 2017 | 149 |
| 2018 | 78 |
| 2019 | 122 |
| 2020 | 109 |
| 2021 | 120 |
| 2022 | 244 |
| 2023 | 201 |
| 2024 | 20 |
| Total | 3818 |