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         1681        614 
1994         2351        848 
1995         4454       1537 
1996         3611       1268 
1997         2350        801 
1998        23404       9862 
1999        14706       5644 
2000        41057      17055 
2001        42191      16473 
2002        33557      14973 
2003        62720      25990 
2004        49350      18946 
2005        88681      27208 
2006       114901      36605 
2007       210377      64307 
2008       131816      37417 
2009       107345      30109 
2010       124883      34602 
2011       188122      52014 
2012       174905      48365 
2013       272123      77102 
2014       673826     171881 
2015       772011     205078 
2016       550516     148203 
2017       472610     135010 
2018       405855     114043 
2019       807208     197505 
2020       719887     184896 
2021       936188     225323 
2022       710323     203254 
2023       562642     161016