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        23376       9852 
1999        14667       5628 
2000        40984      17023 
2001        42099      16436 
2002        33430      14918 
2003        62563      25926 
2004        49239      18901 
2005        88247      27079 
2006       114274      36429 
2007       209659      64112 
2008       131063      37213 
2009       106745      29948 
2010       123830      34315 
2011       187385      51779 
2012       173346      47938 
2013       270754      76725 
2014       671253     171202 
2015       784463     207882 
2016       567099     152197 
2017       528879     147483 
2018       412273     115742 
2019       907799     221779 
2020       725936     186448 
2021       933820     224758 
2022       706607     202128 
2023       638347     183851