Year | Value | 2021 | 28,120 | 2020 | 28,120 | 2019 | 28,115.728 | 2018 | 28,116 | 2017 | 27,602 | 2016 | 27,500 | 2015 | 27,400 | 2014 | 27,400 | 2013 | 27,400 | 2012 | 27,400 | 2011 | 27,300 | 2010 | 26,200 | 2009 | 26,100 | 2008 | 25,950 | 2007 | 23,900 | 2006 | 24,400 | 2005 | 25,100 | 2004 | 23,100 | 2003 | 23,700 | 2002 | 23,560 | 2001 | 23,510 | 2000 | 23,500 | 1999 | 23,450 | 1998 | 23,290 | 1997 | 23,280 | 1996 | 23,270 | 1995 | 23,260 | 1994 | 23,230 | 1993 | 23,200 | 1992 | 23,440 | 1991 | 23,420 | 1990 | 23,390 | 1989 | 23,400 | 1988 | 23,370 | 1987 | 23,340 | 1986 | 23,260 | 1985 | 23,150 | 1984 | 23,110 | 1983 | 23,080 | 1982 | 22,960 | 1981 | 23,490 | 1980 | 23,490 | 1979 | 23,590 | 1978 | 24,690 | 1977 | 24,330 | 1976 | 23,960 | 1975 | 23,590 | 1974 | 23,570 | 1973 | 23,510 | 1972 | 23,450 | 1971 | 23,390 | 1970 | 23,330 | 1969 | 23,280 | 1968 | 23,210 | 1967 | 22,550 | 1966 | 22,050 | 1965 | 21,560 | 1964 | 21,030 | 1963 | 20,600 | 1962 | 17,070 | 1961 | 17,230 |
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