Year | Value | 2021 | 24,290 | 2020 | 24,290 | 2019 | 24,290 | 2018 | 24,290 | 2017 | 24,290 | 2016 | 24,290 | 2015 | 24,290 | 2014 | 23,520 | 2013 | 23,520 | 2012 | 23,520 | 2011 | 23,970 | 2010 | 23,970 | 2009 | 23,970 | 2008 | 23,970 | 2007 | 24,170 | 2006 | 24,170 | 2005 | 24,170 | 2004 | 24,170 | 2003 | 24,350 | 2002 | 25,150 | 2001 | 25,150 | 2000 | 25,150 | 1999 | 24,670 | 1998 | 25,100 | 1997 | 25,000 | 1996 | 25,750 | 1995 | 25,760 | 1994 | 25,460 | 1993 | 25,460 | 1992 | 25,460 | 1991 | 25,460 | 1990 | 25,460 | 1989 | 26,410 | 1988 | 26,370 | 1987 | 26,370 | 1986 | 26,370 | 1985 | 26,300 | 1984 | 26,300 | 1983 | 26,300 | 1982 | 26,300 | 1981 | 26,250 | 1980 | 26,200 | 1979 | 25,900 | 1978 | 25,650 | 1977 | 25,400 | 1976 | 25,100 | 1975 | 24,550 | 1974 | 24,250 | 1973 | 24,050 | 1972 | 23,700 | 1971 | 23,440 | 1970 | 23,350 | 1969 | 23,300 | 1968 | 22,900 | 1967 | 22,800 | 1966 | 22,650 | 1965 | 22,500 | 1964 | 22,350 | 1963 | 22,200 | 1962 | 22,050 | 1961 | 21,900 |
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