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         3608       1267 
1997         2344        799 
1998        23378       9853 
1999        14677       5632 
2000        40986      17024 
2001        42104      16438 
2002        33449      14927 
2003        62589      25937 
2004        49251      18907 
2005        88296      27093 
2006       114336      36447 
2007       209723      64130 
2008       131183      37245 
2009       106798      29962 
2010       123973      34360 
2011       187503      51809 
2012       173535      47990 
2013       270869      76756 
2014       671584     171287 
2015       784771     207957 
2016       565648     151878 
2017       527667     147264 
2018       412382     115771 
2019       906166     221401 
2020       726226     186533 
2021       934214     224833 
2022       707893     202562 
2023       643439     184804