| Year | Value | | 2024 | 20,147 | | 2023 | 20,062 | | 2022 | 19,942 | | 2021 | 19,800 | | 2020 | 19,631 | | 2019 | 19,335 | | 2018 | 18,740 | | 2017 | 18,012 | | 2016 | 17,260 | | 2015 | 16,013 | | 2014 | 14,497 | | 2013 | 13,498 | | 2012 | 12,927 | | 2011 | 12,733 | | 2010 | 13,309 | | 2009 | 14,299 | | 2008 | 15,103 | | 2007 | 15,694 | | 2006 | 16,041 | | 2005 | 16,051 | | 2004 | 15,756 | | 2003 | 15,337 | | 2002 | 14,879 | | 2001 | 14,459 | | 2000 | 14,079 | | 1999 | 13,841 | | 1998 | 13,686 | | 1997 | 13,592 | | 1996 | 13,500 | | 1995 | 13,325 | | 1994 | 12,982 | | 1993 | 12,468 | | 1992 | 11,844 | | 1991 | 11,218 | | 1990 | 10,645 | | 1989 | 10,067 | | 1988 | 9,389 | | 1987 | 8,638 | | 1986 | 7,930 | | 1985 | 7,411 | | 1984 | 7,234 | | 1983 | 7,537 | | 1982 | 8,315 | | 1981 | 9,288 | | 1980 | 10,111 | | 1979 | 10,532 | | 1978 | 10,407 | | 1977 | 9,831 | | 1976 | 9,132 | | 1975 | 8,566 |
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