| Year | Value | | 2022 | 23,967 | | 2021 | 23,416 | | 2020 | 22,744 | | 2019 | 22,274 | | 2018 | 22,028 | | 2017 | 21,640 | | 2016 | 21,148 | | 2015 | 20,639 | | 2014 | 19,721 | | 2013 | 18,579 | | 2012 | 17,864 | | 2011 | 17,487 | | 2010 | 17,388 | | 2009 | 17,589 | | 2008 | 18,003 | | 2007 | 18,474 | | 2006 | 18,988 | | 2005 | 19,508 | | 2004 | 19,907 | | 2003 | 20,169 | | 2002 | 20,284 | | 2001 | 20,252 | | 2000 | 20,082 | | 1999 | 19,811 | | 1998 | 19,467 | | 1997 | 19,102 | | 1996 | 18,759 | | 1995 | 18,430 | | 1994 | 18,081 | | 1993 | 17,744 | | 1992 | 17,438 | | 1991 | 17,157 | | 1990 | 16,899 | | 1989 | 16,659 | | 1988 | 16,423 | | 1987 | 16,169 | | 1986 | 15,880 | | 1985 | 15,539 | | 1984 | 15,142 | | 1983 | 14,697 | | 1982 | 14,224 | | 1981 | 13,748 | | 1980 | 13,290 | | 1979 | 12,853 | | 1978 | 12,439 | | 1977 | 12,057 | | 1976 | 11,711 | | 1975 | 11,421 | | 1974 | 11,211 | | 1973 | 11,075 | | 1972 | 10,994 | | 1971 | 10,954 | | 1970 | 10,912 | | 1969 | 10,837 | | 1968 | 10,729 | | 1967 | 10,584 | | 1966 | 10,394 | | 1965 | 10,177 | | 1964 | 9,940 | | 1963 | 9,663 | | 1962 | 9,338 | | 1961 | 8,950 | | 1960 | 8,498 |
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