| Year | Value | | 2022 | 17,554 | | 2021 | 17,671 | | 2020 | 17,943 | | 2019 | 18,389 | | 2018 | 18,997 | | 2017 | 19,690 | | 2016 | 20,356 | | 2015 | 20,902 | | 2014 | 21,275 | | 2013 | 21,475 | | 2012 | 21,527 | | 2011 | 21,490 | | 2010 | 21,250 | | 2009 | 20,758 | | 2008 | 20,114 | | 2007 | 19,338 | | 2006 | 18,483 | | 2005 | 17,633 | | 2004 | 16,840 | | 2003 | 16,133 | | 2002 | 15,540 | | 2001 | 15,062 | | 2000 | 14,693 | | 1999 | 14,450 | | 1998 | 14,334 | | 1997 | 14,314 | | 1996 | 14,369 | | 1995 | 14,484 | | 1994 | 14,634 | | 1993 | 14,828 | | 1992 | 15,084 | | 1991 | 15,232 | | 1990 | 15,156 | | 1989 | 14,985 | | 1988 | 14,759 | | 1987 | 14,432 | | 1986 | 14,011 | | 1985 | 13,517 | | 1984 | 12,979 | | 1983 | 12,429 | | 1982 | 11,862 | | 1981 | 11,214 | | 1980 | 10,489 | | 1979 | 9,772 | | 1978 | 9,103 | | 1977 | 8,479 | | 1976 | 7,894 | | 1975 | 7,346 | | 1974 | 6,845 | | 1973 | 6,408 | | 1972 | 6,046 | | 1971 | 5,706 | | 1970 | 5,342 | | 1969 | 5,002 | | 1968 | 4,712 | | 1967 | 4,457 | | 1966 | 4,224 | | 1965 | 4,017 | | 1964 | 3,844 | | 1963 | 3,706 | | 1962 | 3,591 | | 1961 | 3,482 | | 1960 | 3,359 |
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