| Year | Value | | 2022 | 20,324 | | 2021 | 19,728 | | 2020 | 19,346 | | 2019 | 19,205 | | 2018 | 19,206 | | 2017 | 19,280 | | 2016 | 19,357 | | 2015 | 19,552 | | 2014 | 19,972 | | 2013 | 20,748 | | 2012 | 21,906 | | 2011 | 22,994 | | 2010 | 23,687 | | 2009 | 24,001 | | 2008 | 23,982 | | 2007 | 23,809 | | 2006 | 23,756 | | 2005 | 23,727 | | 2004 | 23,352 | | 2003 | 22,355 | | 2002 | 20,800 | | 2001 | 19,101 | | 2000 | 17,524 | | 1999 | 16,229 | | 1998 | 15,218 | | 1997 | 14,340 | | 1996 | 13,473 | | 1995 | 12,490 | | 1994 | 11,220 | | 1993 | 9,769 | | 1992 | 8,410 | | 1991 | 7,265 | | 1990 | 6,372 | | 1989 | 5,789 | | 1988 | 5,494 | | 1987 | 5,347 | | 1986 | 5,214 | | 1985 | 5,066 | | 1984 | 4,944 | | 1983 | 4,849 | | 1982 | 4,803 | | 1981 | 4,843 | | 1980 | 5,026 | | 1979 | 5,305 | | 1978 | 5,577 | | 1977 | 5,807 | | 1976 | 5,966 | | 1975 | 6,044 | | 1974 | 6,056 | | 1973 | 6,027 | | 1972 | 5,968 | | 1971 | 5,880 | | 1970 | 5,700 | | 1969 | 5,459 | | 1968 | 5,276 | | 1967 | 5,130 | | 1966 | 4,983 | | 1965 | 4,845 | | 1964 | 4,755 | | 1963 | 4,662 | | 1962 | 4,581 | | 1961 | 4,584 | | 1960 | 4,776 |
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