Year | Value | 2021 | 18,110 | 2020 | 17,860 | 2019 | 17,760 | 2018 | 17,825 | 2017 | 17,810 | 2016 | 17,770 | 2015 | 17,915 | 2014 | 17,850 | 2013 | 18,010 | 2012 | 18,120 | 2011 | 18,190 | 2010 | 18,190 | 2009 | 18,160 | 2008 | 17,930 | 2007 | 18,000 | 2006 | 18,150 | 2005 | 18,050 | 2004 | 18,220 | 2003 | 18,290 | 2002 | 18,260 | 2001 | 18,330 | 2000 | 18,400 | 1999 | 18,880 | 1998 | 19,150 | 1997 | 19,530 | 1996 | 19,950 | 1995 | 20,480 | 1994 | 20,950 | 1993 | 21,130 | 1992 | 21,600 | 1991 | 22,036.18 | 1990 | 21,986 | 1989 | 23,780 | 1988 | 24,630 | 1987 | 25,390 | 1986 | 26,120 | 1985 | 26,810 | 1984 | 27,480 | 1983 | 26,820 | 1982 | 26,790 | 1981 | 25,990 | 1980 | 25,160 | 1979 | 24,430 | 1978 | 23,600 | 1977 | 22,870 | 1976 | 22,050 | 1975 | 21,220 | 1974 | 20,480 | 1973 | 20,480 | 1972 | 18,870 | 1971 | 18,870 | 1970 | 18,560 | 1969 | 17,900 | 1968 | 17,160 | 1967 | 16,360 | 1966 | 16,350 | 1965 | 15,550 | 1964 | 14,850 | 1963 | 14,200 | 1962 | 14,100 | 1961 | 13,950 |
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