| Year | Value | | 2024 | 19,243 | | 2023 | 19,300 | | 2022 | 19,368 | | 2021 | 19,500 | | 2020 | 19,540 | | 2019 | 19,601 | | 2018 | 19,875 | | 2017 | 20,300 | | 2016 | 20,843 | | 2015 | 21,519 | | 2014 | 22,279 | | 2013 | 22,947 | | 2012 | 23,332 | | 2011 | 23,430 | | 2010 | 23,437 | | 2009 | 23,402 | | 2008 | 23,276 | | 2007 | 23,107 | | 2006 | 22,909 | | 2005 | 22,657 | | 2004 | 22,356 | | 2003 | 22,003 | | 2002 | 21,646 | | 2001 | 21,519 | | 2000 | 21,528 | | 1999 | 21,728 | | 1998 | 22,085 | | 1997 | 22,564 | | 1996 | 23,040 | | 1995 | 23,544 | | 1994 | 24,046 | | 1993 | 24,474 | | 1992 | 24,837 | | 1991 | 25,152 | | 1990 | 25,510 | | 1989 | 25,946 | | 1988 | 26,408 | | 1987 | 26,813 | | 1986 | 27,098 | | 1985 | 27,254 | | 1984 | 27,269 | | 1983 | 27,083 | | 1982 | 26,651 | | 1981 | 26,046 | | 1980 | 25,440 | | 1979 | 24,838 | | 1978 | 24,098 | | 1977 | 23,229 | | 1976 | 22,130 | | 1975 | 20,565 |
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