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         4451       1536 
1996         3608       1267 
1997         2344        799 
1998        23378       9853 
1999        14677       5632 
2000        40986      17024 
2001        42108      16440 
2002        33449      14927 
2003        62593      25939 
2004        49253      18908 
2005        88316      27099 
2006       114372      36457 
2007       209734      64133 
2008       131191      37247 
2009       106822      29968 
2010       123999      34367 
2011       187519      51814 
2012       173569      47999 
2013       270912      76768 
2014       671662     171309 
2015       769662     204445 
2016       564743     151698 
2017       522504     146416 
2018       412462     115794 
2019       905678     221284 
2020       726348     186566 
2021       934274     224851 
2022       708064     202608 
2023       615341     176605