Year | Value | 2021 | 2,038 | 2020 | 4,225.333 | 2019 | 10,600 | 2018 | 10,170 | 2017 | 7,650 | 2016 | 7,230 | 2015 | 8,852 | 2014 | 10,385 | 2013 | 9,451 | 2012 | 13,267 | 2011 | 12,332.727272727 | 2010 | 11,714 | 2009 | 9,566 | 2008 | 11,861 | 2007 | 37,310 | 2006 | 14,142 | 2005 | 17,911 | 2004 | 18,016 | 2003 | 17,202 | 2002 | 9,433 | 2001 | 20,129 | 2000 | 20,491 | 1999 | 18,600 | 1998 | 18,300 | 1997 | 16,800 | 1996 | 17,200 | 1995 | 17,800 | 1994 | 16,200 | 1993 | 16,900 | 1992 | 15,300 | 1991 | 14,300 | 1990 | 17,200 | 1989 | 15,300 | 1988 | 16,100 | 1987 | 15,700 | 1986 | 15,600 | 1985 | 16,200 | 1984 | 16,500 | 1983 | 15,000 | 1982 | 15,100 | 1981 | 21,000 | 1980 | 24,500 | 1979 | 23,900 | 1978 | 24,300 | 1977 | 23,100 | 1976 | 20,500 | 1975 | 16,600 | 1974 | 16,500 | 1973 | 16,000 | 1972 | 16,200 | 1971 | 17,600 | 1970 | 17,600 |
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