| Year | Value | | 2021 | 8.5091141038619 | | 2020 | 8.5594960931562 | | 2019 | 9.0413364192021 | | 2018 | 9.5252507901432 | | 2017 | 9.8247487898812 | | 2016 | 9.627286226724 | | 2015 | 9.9066603069222 | | 2014 | 10.185421079864 | | 2013 | 10.440366483009 | | 2012 | 10.693115450839 | | 2011 | 10.747960125432 | | 2010 | 10.527653920798 | | 2009 | 10.641881077182 | | 2008 | 10.691844891128 | | 2007 | 10.177701819428 | | 2006 | 9.5598245849111 | | 2005 | 9.057736518458 |
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