| Year | Value | | 2018 | 4,040.0090080296 | | 2017 | 3,909.9409809912 | | 2016 | 3,635.6931082077 | | 2015 | 3,982.8871218239 | | 2014 | 4,045.6948829099 | | 2013 | 4,156.8473594478 | | 2012 | 4,321.3055628279 | | 2011 | 3,834.1950459187 | | 2010 | 3,347.9321584162 | | 2009 | 2,896.0079587454 | | 2008 | 3,172.3347168514 | | 2007 | 2,758.0338832696 | | 2006 | 2,707.1563729611 | | 2005 | 2,382.3250653721 | | 2004 | 2,124.6465512267 | | 2003 | 1,885.956259135 | | 2002 | 1,727.244723042 | | 2001 | 1,675.2341225533 | | 2000 | 1,882.8096682367 | | 1999 | 1,876.9531521003 | | 1998 | 1,859.9430698503 | | 1997 | 2,069.8136027342 | | 1996 | 2,142.3467356261 | | 1995 | 1,970.7538504873 | | 1994 | 1,964.9148537181 | | 1993 | 1,364.9801415286 | | 1992 | 1,355.2695772614 | | 1991 | 1,319.7048503076 | | 1990 | 1,140.6535956158 | | 1989 | 1,088.9657523505 | | 1988 | 1,129.2200777763 | | 1987 | 842.99219036308 | | 1986 | 715.42712546396 | | 1985 | 624.03172036325 | | 1984 | 664.24546134364 | | 1983 | 627.45121271047 | | 1982 | 655.9838215286 | | 1981 | 664.0335853771 |
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