| Year | Value | | 2021 | 39.941143303726 | | 2020 | 24.031495637676 | | 2019 | 37.350147579138 | | 2018 | 40.281070230868 | | 2017 | 32.102130573335 | | 2016 | 24.444971949318 | | 2015 | 25.071538670789 | | 2014 | 37.9756367322 | | 2013 | 41.385484071984 | | 2012 | 41.711428173707 | | 2011 | 42.747789501016 | | 2010 | 35.978253864507 | | 2009 | 27.672559952749 | | 2008 | 52.507642212667 | | 2007 | 38.846082446921 | | 2006 | 41.00552240919 | | 2005 | 39.922124795889 |
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