*Excludes Observations that spanned multiple years
| Pre 1970 | 115 |
|---|---|
| 1970 | 3 |
| 1971 | 7 |
| 1972 | 3 |
| 1973 | 2 |
| 1974 | 2 |
| 1975 | 2 |
| 1976 | 16 |
| 1977 | 9 |
| 1978 | 3 |
| 1979 | 6 |
| 1980 | 6 |
| 1981 | 10 |
| 1982 | 1 |
| 1983 | 13 |
| 1984 | 3 |
| 1985 | 5 |
| 1986 | 30 |
| 1987 | 4 |
| 1988 | 9 |
| 1989 | 18 |
| 1990 | 7 |
| 1991 | 59 |
| 1992 | 43 |
| 1993 | 38 |
| 1994 | 63 |
| 1995 | 77 |
| 1996 | 18 |
| 1997 | 38 |
| 1998 | 81 |
| 1999 | 39 |
| 2000 | 12 |
| 2001 | 169 |
| 2002 | 91 |
| 2003 | 99 |
| 2004 | 340 |
| 2005 | 75 |
| 2006 | 327 |
| 2007 | 836 |
| 2008 | 339 |
| 2009 | 429 |
| 2010 | 411 |
| 2011 | 564 |
| 2012 | 285 |
| 2013 | 159 |
| 2014 | 245 |
| 2015 | 516 |
| 2016 | 331 |
| 2017 | 629 |
| 2018 | 1066 |
| 2019 | 464 |
| 2020 | 788 |
| 2021 | 869 |
| 2022 | 313 |
| 2023 | 360 |
| 2024 | 55 |
| Total | 10502 |