Year | Value | 2021 | 21,813.16 | 2020 | 21,741 | 2019 | 21,830 | 2018 | 21,930 | 2017 | 22,030 | 2016 | 22,130 | 2015 | 22,230 | 2014 | 22,330 | 2013 | 22,430 | 2012 | 22,530 | 2011 | 22,630 | 2010 | 22,663.9 | 2009 | 22,316 | 2008 | 22,292 | 2007 | 22,318 | 2006 | 22,244 | 2005 | 22,300 | 2004 | 22,326 | 2003 | 22,352 | 2002 | 22,378 | 2001 | 22,404 | 2000 | 22,300 | 1999 | 21,570 | 1998 | 21,490 | 1997 | 21,400 | 1996 | 21,320 | 1995 | 21,320 | 1994 | 21,350 | 1993 | 21,500 | 1992 | 21,500 | 1991 | 21,340 | 1990 | 21,240 | 1989 | 21,000 | 1988 | 20,700 | 1987 | 20,450 | 1986 | 20,200 | 1985 | 19,950 | 1984 | 19,660 | 1983 | 19,410 | 1982 | 19,140 | 1981 | 18,820 | 1980 | 18,550 | 1979 | 18,520 | 1978 | 18,500 | 1977 | 18,490 | 1976 | 18,270 | 1975 | 18,060 | 1974 | 17,850 | 1973 | 17,630 | 1972 | 17,430 | 1971 | 17,130 | 1970 | 16,840 | 1969 | 16,870 | 1968 | 16,790 | 1967 | 16,690 | 1966 | 16,680 | 1965 | 16,580 | 1964 | 16,480 | 1963 | 16,440 | 1962 | 16,340 | 1961 | 16,240 |
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