| Year | Value | | 2021 | 6.5039778805898 | | 2020 | -2.3022971512549 | | 2019 | 3.2875298526356 | | 2018 | 3.5533460028241 | | 2017 | 5.5832273028628 | | 2016 | 5.1075370810863 | | 2015 | 4.164489787136 | | 2014 | 5.0189476716571 | | 2013 | 4.5543054201045 | | 2012 | 5.9253149125918 | | 2011 | 4.9642432944029 | | 2010 | 8.118682221821 | | 2009 | 4.6871369925167 | | 2008 | 4.1352353763827 | | 2007 | 15.285929836126 | | 2006 | 11.507285410518 | | 2005 | 6.8720979212505 | | 2004 | 12.758447133792 | | 2003 | 0.27141308334196 | | 2002 | 13.099935562789 | | 2001 | 3.6135157006805 | | 2000 | 3.1591283088188 | | 1999 | 2.0347805082321 | | 1998 | -4.3507262145459 | | 1997 | 4.146671927903 | | 1996 | 0.27951062227376 |
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