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          492        186 
1992          770        310 
1993         1356        504 
1994         2228        805 
1995         3359       1168 
1996         3570       1254 
1997         2326        793 
1998        23228       9795 
1999        14500       5560 
2000        40381      16754 
2001        42882      16627 
2002        32395      14481 
2003        60903      25260 
2004        47783      18329 
2005        84593      26016 
2006       109760      35095 
2007       202147      62061 
2008       123330      35121 
2009       100152      28166 
2010       116556      32403 
2011       173830      48095 
2012       161594      44721 
2013       247153      70156 
2014       589611     151445 
2015       715422     189806 
2016       701170     181441 
2017       597198     161276 
2018       392283     109936 
2019       926107     227421 
2020       676716     173278 
2021       888823     212577 
2022       660504     188900 
2023       612619     173601 
2024       269421      78105