| Year | Value | | 2022 | 20,647 | | 2021 | 20,674 | | 2020 | 20,678 | | 2019 | 20,241 | | 2018 | 19,503 | | 2017 | 18,758 | | 2016 | 18,040 | | 2015 | 17,363 | | 2014 | 16,712 | | 2013 | 16,052 | | 2012 | 15,394 | | 2011 | 14,789 | | 2010 | 14,252 | | 2009 | 13,772 | | 2008 | 13,358 | | 2007 | 12,995 | | 2006 | 12,627 | | 2005 | 12,239 | | 2004 | 11,849 | | 2003 | 11,444 | | 2002 | 11,030 | | 2001 | 10,687 | | 2000 | 10,457 | | 1999 | 10,334 | | 1998 | 10,345 | | 1997 | 10,455 | | 1996 | 10,591 | | 1995 | 10,725 | | 1994 | 10,857 | | 1993 | 10,993 | | 1992 | 11,134 | | 1991 | 11,329 | | 1990 | 11,611 | | 1989 | 11,980 | | 1988 | 12,440 | | 1987 | 12,393 | | 1986 | 11,788 | | 1985 | 11,179 | | 1984 | 10,584 | | 1983 | 10,007 | | 1982 | 9,425 | | 1981 | 8,823 | | 1980 | 8,201 | | 1979 | 7,549 | | 1978 | 6,857 | | 1977 | 6,123 | | 1976 | 5,350 | | 1975 | 4,544 | | 1974 | 4,095 | | 1973 | 4,040 | | 1972 | 4,002 | | 1971 | 3,950 | | 1970 | 3,871 | | 1969 | 3,764 | | 1968 | 3,620 | | 1967 | 3,452 | | 1966 | 3,295 | | 1965 | 3,178 | | 1964 | 3,113 | | 1963 | 3,101 | | 1962 | 3,143 | | 1961 | 3,217 | | 1960 | 3,307 |
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