Year | Value | 2021 | 756 | 2020 | 2,123 | 2019 | 7,146 | 2018 | 8,830 | 2017 | 13,144 | 2016 | 20,058 | 2015 | 17,592 | 2014 | 15,468 | 2013 | 23,292 | 2012 | 15,869.772204784 | 2011 | 18,302.858370897 | 2010 | 21,235.450280909 | 2009 | 10,653 | 2008 | 11,686 | 2007 | 11,874 | 2006 | 11,533 | 2005 | 11,484 | 2004 | 10,937 | 2003 | 8,998 | 2002 | 9,773 | 2001 | 11,728 | 2000 | 12,264 | 1999 | 15,700 | 1998 | 19,700 | 1997 | 16,800 | 1996 | 14,400 | 1995 | 12,800 | 1994 | 12,500 | 1993 | 8,600 | 1992 | 9,900 | 1991 | 12,000 | 1990 | 19,400 | 1989 | 18,900 | 1988 | 17,600 | 1987 | 19,400 | 1986 | 18,700 | 1985 | 16,000 | 1984 | 17,100 | 1983 | 20,300 | 1982 | 18,000 | 1981 | 15,900 | 1980 | 17,200 | 1979 | 17,500 | 1978 | 17,100 | 1977 | 13,300 | 1976 | 17,100 | 1975 | 15,800 | 1974 | 15,200 | 1973 | 17,400 | 1972 | 19,400 | 1971 | 17,900 | 1970 | 15,600 |
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