| Year | Value | | 2024 | 18,776 | | 2023 | 19,040 | | 2022 | 19,360 | | 2021 | 19,646 | | 2020 | 19,800 | | 2019 | 19,941 | | 2018 | 20,142 | | 2017 | 20,266 | | 2016 | 20,317 | | 2015 | 20,404 | | 2014 | 20,507 | | 2013 | 20,471 | | 2012 | 20,309 | | 2011 | 19,993 | | 2010 | 19,533 | | 2009 | 18,906 | | 2008 | 18,015 | | 2007 | 17,086 | | 2006 | 16,146 | | 2005 | 14,797 | | 2004 | 13,365 | | 2003 | 12,393 | | 2002 | 11,760 | | 2001 | 11,634 | | 2000 | 12,199 | | 1999 | 13,160 | | 1998 | 14,097 | | 1997 | 14,872 | | 1996 | 15,358 | | 1995 | 15,546 | | 1994 | 15,471 | | 1993 | 15,232 | | 1992 | 14,941 | | 1991 | 14,715 | | 1990 | 14,583 | | 1989 | 14,523 | | 1988 | 14,480 | | 1987 | 14,386 | | 1986 | 14,122 | | 1985 | 13,604 | | 1984 | 12,852 | | 1983 | 11,924 | | 1982 | 10,925 | | 1981 | 10,018 | | 1980 | 9,268 | | 1979 | 8,573 | | 1978 | 7,799 | | 1977 | 6,958 | | 1976 | 6,186 | | 1975 | 5,622 |
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