| Year | Value | | 2024 | 18,714 | | 2023 | 18,820 | | 2022 | 18,912 | | 2021 | 19,035 | | 2020 | 19,041 | | 2019 | 19,132 | | 2018 | 19,450 | | 2017 | 19,902 | | 2016 | 20,484 | | 2015 | 21,204 | | 2014 | 21,927 | | 2013 | 22,582 | | 2012 | 23,087 | | 2011 | 23,335 | | 2010 | 23,575 | | 2009 | 23,834 | | 2008 | 23,904 | | 2007 | 23,822 | | 2006 | 23,738 | | 2005 | 23,703 | | 2004 | 23,621 | | 2003 | 23,441 | | 2002 | 23,195 | | 2001 | 22,935 | | 2000 | 22,622 | | 1999 | 22,519 | | 1998 | 22,527 | | 1997 | 22,593 | | 1996 | 22,757 | | 1995 | 22,977 | | 1994 | 23,222 | | 1993 | 23,491 | | 1992 | 23,744 | | 1991 | 24,020 | | 1990 | 24,438 | | 1989 | 24,941 | | 1988 | 25,364 | | 1987 | 25,669 | | 1986 | 25,858 | | 1985 | 25,925 | | 1984 | 25,857 | | 1983 | 25,642 | | 1982 | 25,245 | | 1981 | 24,740 | | 1980 | 24,372 | | 1979 | 24,108 | | 1978 | 23,673 | | 1977 | 23,046 | | 1976 | 22,192 | | 1975 | 20,941 |
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