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        40965      17015 
2001        42086      16430 
2002        33395      14902 
2003        62532      25913 
2004        49204      18887 
2005        88146      27051 
2006       114172      36401 
2007       209539      64080 
2008       130937      37178 
2009       106616      29913 
2010       123677      34274 
2011       187158      51716 
2012       173009      47846 
2013       270491      76653 
2014       670754     171072 
2015       783925     207732 
2016       569906     152846 
2017       529892     147706 
2018       412221     115724 
2019       915766     223697 
2020       725313     186280 
2021       933405     224643 
2022       701628     200711 
2023       656158     188724