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        14668       5629 
2000        40984      17023 
2001        42099      16436 
2002        33434      14920 
2003        62568      25928 
2004        49241      18902 
2005        88263      27084 
2006       114306      36438 
2007       209689      64120 
2008       131107      37225 
2009       106760      29952 
2010       123916      34343 
2011       187444      51794 
2012       173412      47956 
2013       270810      76740 
2014       671451     171255 
2015       784584     207913 
2016       566788     152132 
2017       528729     147461 
2018       412336     115759 
2019       906945     221581 
2020       726089     186493 
2021       934036     224792 
2022       707707     202510 
2023       633172     182411