| Year | Value | | 2024 | 19,062 | | 2023 | 19,096 | | 2022 | 19,270 | | 2021 | 19,656 | | 2020 | 20,267 | | 2019 | 21,025 | | 2018 | 21,782 | | 2017 | 22,325 | | 2016 | 22,621 | | 2015 | 22,757 | | 2014 | 22,732 | | 2013 | 22,556 | | 2012 | 22,270 | | 2011 | 21,934 | | 2010 | 21,648 | | 2009 | 21,420 | | 2008 | 21,125 | | 2007 | 20,784 | | 2006 | 20,577 | | 2005 | 20,414 | | 2004 | 20,198 | | 2003 | 20,165 | | 2002 | 20,350 | | 2001 | 20,573 | | 2000 | 20,941 | | 1999 | 21,537 | | 1998 | 22,137 | | 1997 | 22,732 | | 1996 | 23,237 | | 1995 | 23,639 | | 1994 | 23,956 | | 1993 | 24,201 | | 1992 | 24,361 | | 1991 | 24,501 | | 1990 | 24,714 | | 1989 | 24,987 | | 1988 | 25,195 | | 1987 | 25,249 | | 1986 | 25,093 | | 1985 | 24,695 | | 1984 | 24,012 | | 1983 | 23,030 | | 1982 | 21,853 | | 1981 | 20,572 | | 1980 | 19,120 | | 1979 | 17,604 | | 1978 | 16,372 | | 1977 | 15,585 | | 1976 | 15,337 | | 1975 | 15,758 |
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