| Year | Value | | 2021 | 2.4288696571061 | | 2020 | -3.3594313671745 | | 2019 | 1.2899008879063 | | 2018 | 4.1153070617375 | | 2017 | 3.5414686967106 | | 2016 | 1.1057979164508 | | 2015 | 3.7762889026506 | | 2014 | 2.4718549483082 | | 2013 | 0.97030201679276 | | 2012 | 2.7860185808801 | | 2011 | 0.20913939490698 | | 2010 | 5.4238126239221 | | 2009 | -5.7091417398229 | | 2008 | 5.6673029331622 | | 2007 | 11.694614790867 | | 2006 | 9.0266668057034 | | 2005 | 10.525509562667 | | 2004 | 9.3959248203743 | | 2003 | 0.8868975548138 | | 2002 | 5.9717092479095 | | 2001 | 5.4395622239327 | | 2000 | 2.6407604168955 | | 1999 | 0.28100624741654 | | 1998 | 5.3206107483503 | | 1997 | 8.9982062356804 | | 1996 | 7.5508243560894 |
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