| Year | Value | | 2024 | 21,391 | | 2023 | 21,438 | | 2022 | 21,430 | | 2021 | 21,356 | | 2020 | 21,270 | | 2019 | 21,232 | | 2018 | 21,074 | | 2017 | 20,809 | | 2016 | 20,462 | | 2015 | 20,128 | | 2014 | 19,801 | | 2013 | 19,255 | | 2012 | 18,612 | | 2011 | 17,962 | | 2010 | 16,767 | | 2009 | 15,255 | | 2008 | 14,227 | | 2007 | 13,614 | | 2006 | 13,457 | | 2005 | 14,100 | | 2004 | 15,185 | | 2003 | 16,104 | | 2002 | 16,673 | | 2001 | 16,947 | | 2000 | 16,900 | | 1999 | 16,655 | | 1998 | 16,321 | | 1997 | 15,980 | | 1996 | 15,662 | | 1995 | 15,374 | | 1994 | 15,147 | | 1993 | 14,992 | | 1992 | 14,886 | | 1991 | 14,761 | | 1990 | 14,547 | | 1989 | 14,184 | | 1988 | 13,667 | | 1987 | 13,039 | | 1986 | 12,380 | | 1985 | 11,724 | | 1984 | 11,019 | | 1983 | 10,203 | | 1982 | 9,318 | | 1981 | 8,492 | | 1980 | 7,883 | | 1979 | 7,691 | | 1978 | 8,084 | | 1977 | 9,016 | | 1976 | 10,145 | | 1975 | 11,053 |
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