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        23373       9851 
1999        14667       5628 
2000        40978      17021 
2001        42099      16436 
2002        33423      14915 
2003        62561      25925 
2004        49234      18899 
2005        88233      27075 
2006       114263      36426 
2007       209650      64109 
2008       131056      37211 
2009       106735      29945 
2010       123800      34307 
2011       187362      51773 
2012       173296      47924 
2013       270733      76719 
2014       671216     171193 
2015       784420     207868 
2016       567743     152353 
2017       529140     147550 
2018       412332     115756 
2019       908552     221966 
2020       725880     186432 
2021       933770     224743 
2022       705806     201902 
2023       646046     186030