| Year | Value | | 2021 | 2.4744537423697 | | 2020 | -15.92875654567 | | 2019 | 2.8758124175815 | | 2018 | 3.7052236039944 | | 2017 | 4.7107043726527 | | 2016 | 4.2963496011292 | | 2015 | 4.4927586978935 | | 2014 | 4.1595300234564 | | 2013 | 5.971679073689 | | 2012 | 0.028810952795723 | | 2011 | 3.4876315449869 | | 2010 | -1.4316794578992 | | 2009 | -1.4391975947413 | | 2008 | -2.854983894372 | | 2007 | 7.5769881114512 |
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