*Excludes Observations that spanned multiple years
| Pre 1970 | 151 |
|---|---|
| 1970 | 5 |
| 1971 | 6 |
| 1972 | 0 |
| 1973 | 2 |
| 1974 | 1 |
| 1975 | 6 |
| 1976 | 4 |
| 1977 | 5 |
| 1978 | 1 |
| 1979 | 9 |
| 1980 | 3 |
| 1981 | 2 |
| 1982 | 7 |
| 1983 | 3 |
| 1984 | 1 |
| 1985 | 67 |
| 1986 | 34 |
| 1987 | 111 |
| 1988 | 166 |
| 1989 | 35 |
| 1990 | 32 |
| 1991 | 164 |
| 1992 | 170 |
| 1993 | 219 |
| 1994 | 66 |
| 1995 | 250 |
| 1996 | 179 |
| 1997 | 159 |
| 1998 | 24 |
| 1999 | 102 |
| 2000 | 59 |
| 2001 | 79 |
| 2002 | 37 |
| 2003 | 75 |
| 2004 | 100 |
| 2005 | 58 |
| 2006 | 70 |
| 2007 | 101 |
| 2008 | 109 |
| 2009 | 115 |
| 2010 | 119 |
| 2011 | 78 |
| 2012 | 110 |
| 2013 | 113 |
| 2014 | 95 |
| 2015 | 73 |
| 2016 | 101 |
| 2017 | 88 |
| 2018 | 96 |
| 2019 | 217 |
| 2020 | 80 |
| 2021 | 147 |
| 2022 | 142 |
| 2023 | 100 |
| 2024 | 133 |
| 2025 | 110 |
| 2026 | 4 |
| Total | 4593 |