| Year | Value | | 2021 | 4.8892858958946 | | 2020 | -2.3556974403517 | | 2019 | 4.6644984725457 | | 2018 | 4.9337772928112 | | 2017 | 5.5256509789789 | | 2016 | 3.2148764533364 | | 2015 | 4.9017548288153 | | 2014 | 4.08650857227 | | 2013 | 1.4465000931362 | | 2012 | 1.0099042346702 | | 2011 | 2.284235839253 | | 2010 | 0.10897870420624 | | 2009 | -2.8437879458198 | | 2008 | 5.4909118775299 | | 2007 | 7.2292959985339 | | 2006 | 5.8282775729703 | | 2005 | 6.7893605951174 | | 2004 | 6.0486166758815 | | 2003 | 3.4571486335123 | | 2002 | 4.3716639091747 | | 2001 | 3.9378535407257 | | 2000 | 3.217483054656 | | 1999 | 1.5861592721061 | | 1998 | 4.6927888303879 | | 1997 | 2.6132566533876 | | 1996 | 4.1297295468826 |
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