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         4445       1534 
1996         3605       1266 
1997         2340        798 
1998        23370       9850 
1999        14665       5627 
2000        40963      17014 
2001        42079      16427 
2002        33390      14900 
2003        62517      25907 
2004        49188      18880 
2005        88117      27043 
2006       114133      36390 
2007       209489      64066 
2008       130900      37168 
2009       106584      29904 
2010       123623      34259 
2011       187037      51683 
2012       172926      47823 
2013       270366      76619 
2014       670592     171024 
2015       783710     207678 
2016       570505     152983 
2017       530275     147748 
2018       412096     115693 
2019       917178     224067 
2020       725142     186233 
2021       933279     224617 
2022       700944     200516 
2023       658468     189371