*Excludes Observations that spanned multiple years
| Pre 1970 | 47 |
|---|---|
| 1970 | 0 |
| 1971 | 1 |
| 1972 | 1 |
| 1973 | 1 |
| 1974 | 0 |
| 1975 | 0 |
| 1976 | 0 |
| 1977 | 1 |
| 1978 | 0 |
| 1979 | 1 |
| 1980 | 3 |
| 1981 | 4 |
| 1982 | 0 |
| 1983 | 0 |
| 1984 | 1 |
| 1985 | 2 |
| 1986 | 4 |
| 1987 | 12 |
| 1988 | 3 |
| 1989 | 4 |
| 1990 | 34 |
| 1991 | 12 |
| 1992 | 18 |
| 1993 | 27 |
| 1994 | 70 |
| 1995 | 57 |
| 1996 | 52 |
| 1997 | 34 |
| 1998 | 46 |
| 1999 | 181 |
| 2000 | 439 |
| 2001 | 205 |
| 2002 | 279 |
| 2003 | 1957 |
| 2004 | 1189 |
| 2005 | 877 |
| 2006 | 741 |
| 2007 | 734 |
| 2008 | 1023 |
| 2009 | 6271 |
| 2010 | 1345 |
| 2011 | 1329 |
| 2012 | 1270 |
| 2013 | 1135 |
| 2014 | 1341 |
| 2015 | 707 |
| 2016 | 818 |
| 2017 | 1154 |
| 2018 | 633 |
| 2019 | 399 |
| 2020 | 565 |
| 2021 | 1259 |
| 2022 | 2932 |
| 2023 | 602 |
| 2024 | 0 |
| Total | 29820 |