*Excludes Observations that spanned multiple years
| Pre 1970 | 78 |
|---|---|
| 1970 | 1 |
| 1971 | 1 |
| 1972 | 0 |
| 1973 | 1 |
| 1974 | 3 |
| 1975 | 3 |
| 1976 | 5 |
| 1977 | 4 |
| 1978 | 1 |
| 1979 | 3 |
| 1980 | 18 |
| 1981 | 3 |
| 1982 | 6 |
| 1983 | 8 |
| 1984 | 18 |
| 1985 | 98 |
| 1986 | 96 |
| 1987 | 93 |
| 1988 | 72 |
| 1989 | 65 |
| 1990 | 195 |
| 1991 | 74 |
| 1992 | 84 |
| 1993 | 166 |
| 1994 | 172 |
| 1995 | 341 |
| 1996 | 118 |
| 1997 | 591 |
| 1998 | 849 |
| 1999 | 767 |
| 2000 | 5399 |
| 2001 | 2435 |
| 2002 | 1146 |
| 2003 | 12808 |
| 2004 | 14277 |
| 2005 | 5023 |
| 2006 | 3925 |
| 2007 | 2771 |
| 2008 | 2670 |
| 2009 | 10513 |
| 2010 | 3635 |
| 2011 | 3631 |
| 2012 | 3957 |
| 2013 | 3211 |
| 2014 | 3790 |
| 2015 | 3086 |
| 2016 | 4027 |
| 2017 | 3376 |
| 2018 | 3381 |
| 2019 | 1890 |
| 2020 | 4427 |
| 2021 | 4683 |
| 2022 | 3987 |
| 2023 | 1504 |
| 2024 | 4 |
| Total | 113490 |