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          540        203 
1992          942        370 
1993         1694        619 
1994         2372        856 
1995         4521       1561 
1996         3618       1271 
1997         2385        815 
1998        23451       9882 
1999        14745       5661 
2000        41309      17170 
2001        42442      16583 
2002        33737      15055 
2003        63129      26167 
2004        49722      19088 
2005        89608      27513 
2006       116230      37009 
2007       212137      64791 
2008       133480      37868 
2009       109155      30604 
2010       126833      35129 
2011       190671      52714 
2012       178489      49344 
2013       275809      78159 
2014       680225     173567 
2015       778975     206962 
2016       557215     150157 
2017       479384     137057 
2018       411873     115852 
2019       814605     199804 
2020       725903     186598 
2021       943257     227153 
2022       718356     205541 
2023       549548     156853