| Year | Value | | 2021 | 1,917 | | 2020 | 1,747 | | 2019 | 8,090 | | 2018 | 10,160 | | 2017 | 3,454 | | 2016 | 3,864 | | 2015 | 4,116 | | 2014 | 5,496 | | 2013 | 6,408 | | 2012 | 6,594 | | 2011 | 6,873.7328497082 | | 2010 | 6,459 | | 2009 | 9,758 | | 2008 | 10,522 | | 2007 | 10,351 | | 2006 | 9,807 | | 2005 | 10,059 | | 2004 | 9,104 | | 2003 | 8,557 | | 2002 | 8,497 | | 2001 | 8,173 | | 2000 | 7,556 | | 1999 | 8,000 | | 1998 | 4,400 | | 1997 | 4,200 | | 1996 | 10,200 | | 1995 | 900 | | 1994 | 6,800 | | 1993 | 13,600 | | 1992 | 7,400 | | 1991 | 7,300 | | 1990 | 6,100 | | 1989 | 6,200 | | 1988 | 6,400 | | 1987 | 7,800 | | 1986 | 7,300 | | 1985 | 6,600 | | 1984 | 6,400 | | 1983 | 6,000 | | 1982 | 5,900 | | 1981 | 5,900 | | 1980 | 6,300 | | 1979 | 5,900 | | 1978 | 5,800 | | 1977 | 5,700 | | 1976 | 4,200 | | 1975 | 4,100 | | 1974 | 4,100 | | 1973 | 4,100 | | 1972 | 4,100 | | 1971 | 4,500 | | 1970 | 4,400 |
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