| Year | Value | | 2021 | 9.175648287724 | | 2020 | -2.4579317756149 | | 2019 | 5.2002206132246 | | 2018 | 3.6169923291471 | | 2017 | 5.078839276727 | | 2016 | 5.6443703187237 | | 2015 | 4.3531525785721 | | 2014 | 5.8823552683177 | | 2013 | 6.5342074875896 | | 2012 | 1.687164909659 | | 2011 | 5.1161646131843 | | 2010 | 6.6218302087954 | | 2009 | 2.9125546561735 | | 2008 | 0.66493849246379 | | 2007 | 5.9937306829178 | | 2006 | 6.3267491255237 | | 2005 | 5.7887550837562 | | 2004 | 4.4030848299889 | | 2003 | 0.47566860062575 | | 2002 | 0.86609148935697 | | 2001 | 2.1670704676499 | | 2000 | 6.4223375350399 | | 1999 | 1.8048055553679 | | 1998 | 4.8618744109027 | | 1997 | 4.5168906874763 | | 1996 | 6.373387834458 |
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