Year Observations     Objects
1950            2          1 
1951            6          3 
1953            4          2 
1954            2          1 
1955            4          2 
1956            2          1 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978            8          3 
1981            4          2 
1982           12          6 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990           32         14 
1991          532        200 
1992          936        367 
1993         1678        613 
1994         2342        845 
1995         4448       1535 
1996         3605       1266 
1997         2344        799 
1998        23370       9850 
1999        14665       5627 
2000        40965      17015 
2001        42088      16431 
2002        33401      14905 
2003        62547      25919 
2004        49216      18892 
2005        88179      27061 
2006       114196      36408 
2007       209587      64093 
2008       130973      37188 
2009       106670      29928 
2010       123712      34284 
2011       187232      51737 
2012       173116      47875 
2013       270578      76677 
2014       670886     171110 
2015       784152     207796 
2016       569430     152748 
2017       529664     147669 
2018       412311     115751 
2019       912868     223081 
2020       725514     186333 
2021       933562     224686 
2022       702460     200953 
2023       652550     187789