| Year | Value | | 2024 | 17,264 | | 2023 | 17,455 | | 2022 | 17,583 | | 2021 | 17,739 | | 2020 | 17,919 | | 2019 | 18,088 | | 2018 | 18,278 | | 2017 | 18,415 | | 2016 | 18,411 | | 2015 | 18,501 | | 2014 | 18,724 | | 2013 | 18,872 | | 2012 | 18,945 | | 2011 | 18,936 | | 2010 | 18,722 | | 2009 | 18,487 | | 2008 | 18,531 | | 2007 | 18,799 | | 2006 | 19,199 | | 2005 | 19,568 | | 2004 | 19,777 | | 2003 | 19,899 | | 2002 | 20,002 | | 2001 | 20,162 | | 2000 | 20,395 | | 1999 | 20,774 | | 1998 | 21,146 | | 1997 | 21,510 | | 1996 | 21,892 | | 1995 | 22,378 | | 1994 | 22,997 | | 1993 | 23,686 | | 1992 | 24,395 | | 1991 | 25,035 | | 1990 | 25,377 | | 1989 | 25,491 | | 1988 | 25,634 | | 1987 | 25,800 | | 1986 | 25,948 | | 1985 | 26,197 | | 1984 | 26,495 | | 1983 | 26,734 | | 1982 | 26,962 | | 1981 | 27,151 | | 1980 | 26,985 | | 1979 | 26,594 | | 1978 | 26,359 | | 1977 | 26,228 | | 1976 | 26,124 | | 1975 | 26,137 |
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