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          503        190 
1992          936        367 
1993         1666        609 
1994         2326        839 
1995         3388       1178 
1996         3576       1256 
1997         2329        794 
1998        23263       9808 
1999        14524       5569 
2000        40474      16795 
2001        43050      16693 
2002        32484      14521 
2003        61220      25379 
2004        47963      18395 
2005        85360      26245 
2006       110804      35406 
2007       204018      62567 
2008       125151      35621 
2009       101780      28602 
2010       118284      32855 
2011       177465      49078 
2012       164800      45549 
2013       256005      72335 
2014       606986     155173 
2015       730423     193603 
2016       614834     161521 
2017       603054     162452 
2018       396830     111064 
2019       931772     228366 
2020       686178     175805 
2021       894672     214166 
2022       664255     190000 
2023       603415     173746 
2024       220730      63799