| Year | Value | | 2021 | 6.9333911833589 | | 2020 | -5.3522305507592 | | 2019 | 4.776443095528 | | 2018 | 10.068186835085 | | 2017 | 4.3288169885807 | | 2016 | 4.038086647334 | | 2015 | 6.1409402298194 | | 2014 | 5.9549573643137 | | 2013 | 4.2328082009921 | | 2012 | 7.7808529453357 | | 2011 | 3.0532660505726 | | 2010 | 8.4052278465815 | | 2009 | 1.3427041221981 | | 2008 | 8.0359113996761 | | 2007 | 2.3447215825665 | | 2006 | 4.4610093687374 | | 2005 | 7.3192452892092 | | 2004 | 1.5774911704664 | | 2003 | 1.9199754008808 | | 2002 | 5.5108602700495 | | 2001 | 10.131190043388 | | 2000 | -1.3816663261007 | | 1999 | 0.77021564156534 | | 1998 | 13.412529448223 | | 1997 | 1.9063713269708 | | 1996 | -2.1387722449459 | | 1995 | 6.675308834981 | | 1994 | 2.8275510007017 | | 1993 | 3.928924945609 | | 1992 | -3.0251650930355 | | 1991 | 1.8787588600606 |
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