| Year | Value | | 2021 | 14,410 | | 2020 | 14,180 | | 2019 | 14,040 | | 2018 | 14,050 | | 2017 | 14,050 | | 2016 | 13,280 | | 2015 | 13,220 | | 2014 | 13,050 | | 2013 | 12,860 | | 2012 | 12,860 | | 2011 | 12,860 | | 2010 | 12,670 | | 2009 | 12,670 | | 2008 | 12,450 | | 2007 | 12,120 | | 2006 | 11,510 | | 2005 | 11,330 | | 2004 | 11,230 | | 2003 | 11,080 | | 2002 | 11,030 | | 2001 | 10,930 | | 2000 | 10,880 | | 1999 | 10,810 | | 1998 | 10,640 | | 1997 | 10,230 | | 1996 | 10,160 | | 1995 | 9,940 | | 1994 | 9,780 | | 1993 | 9,710 | | 1992 | 9,420 | | 1991 | 9,330 | | 1990 | 9,280 | | 1989 | 9,060 | | 1988 | 8,870 | | 1987 | 8,620 | | 1986 | 8,560 | | 1985 | 8,280 | | 1984 | 8,070 | | 1983 | 7,920 | | 1982 | 7,950 | | 1981 | 8,030 | | 1980 | 7,970 | | 1979 | 7,930 | | 1978 | 7,830 | | 1977 | 7,580 | | 1976 | 7,450 | | 1975 | 7,260 | | 1974 | 7,040 | | 1973 | 6,770 | | 1972 | 6,580 | | 1971 | 6,480 | | 1970 | 6,240 | | 1969 | 6,070 | | 1968 | 5,870 | | 1967 | 5,680 | | 1966 | 5,470 | | 1965 | 5,500 | | 1964 | 5,500 | | 1963 | 5,210 | | 1962 | 5,170 | | 1961 | 5,070 |
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