| Year | Value | | 2021 | 3,414 | | 2020 | 3,414 | | 2019 | 3,414 | | 2018 | 3,421 | | 2017 | 3,416 | | 2016 | 3,411 | | 2015 | 3,406 | | 2014 | 3,401 | | 2013 | 3,396 | | 2012 | 3,391 | | 2011 | 3,386 | | 2010 | 3,380 | | 2009 | 3,384 | | 2008 | 3,368 | | 2007 | 3,322 | | 2006 | 3,326 | | 2005 | 3,330 | | 2004 | 3,334 | | 2003 | 3,338 | | 2002 | 3,362 | | 2001 | 3,366 | | 2000 | 3,370 | | 1999 | 3,370 | | 1998 | 3,410 | | 1997 | 3,430 | | 1996 | 3,420 | | 1995 | 3,400 | | 1994 | 3,400 | | 1993 | 3,350 | | 1992 | 3,300 | | 1991 | 3,300 | | 1990 | 3,180 | | 1989 | 3,050 | | 1988 | 3,030 | | 1987 | 2,990 | | 1986 | 2,950 | | 1985 | 2,920 | | 1984 | 2,890 | | 1983 | 2,860 | | 1982 | 2,840 | | 1981 | 2,820 | | 1980 | 2,790 | | 1979 | 2,760 | | 1978 | 2,710 | | 1977 | 2,620 | | 1976 | 2,580 | | 1975 | 2,550 | | 1974 | 2,500 | | 1973 | 2,500 | | 1972 | 2,450 | | 1971 | 2,430 | | 1970 | 2,430 | | 1969 | 2,330 | | 1968 | 2,320 | | 1967 | 2,320 | | 1966 | 2,300 | | 1965 | 2,300 | | 1964 | 2,300 | | 1963 | 2,300 | | 1962 | 2,300 | | 1961 | 2,300 |
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