Year Observations     Objects
1858            3          3 
1889            1          1 
1901            1          1 
1920            6          2 
1950            2          1 
1951            6          3 
1953           14          8 
1954           12          5 
1955           14          7 
1956            8          4 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978           12          5 
1981           18          5 
1982           13          7 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990          231         82 
1991          867        310 
1992          721        293 
1993         1280        477 
1994         1628        599 
1995         2881       1008 
1996         2886       1021 
1997         2927        999 
1998        24674      10370 
1999        13483       5143 
2000        37878      15627 
2001        43342      17063 
2002        40587      17022 
2003        60458      24704 
2004        47097      17966 
2005       312500     140349 
2006       338621     150845 
2007       198461      61319 
2008       116343      33240 
2009        97503      27328 
2010       147706      39340 
2011       157139      42911 
2012       185283      41052 
2013       243665      61873 
2014       560905     137406 
2015       811118     209839 
2016       631842     162893 
2017       544752     147603 
2018       331907      93291 
2019       842215     205696 
2020       577799     146339 
2021       788630     186113 
2022       598843     171442 
2023       540990     154791 
2024       594361     170779 
2025       598812     170425