| Year | Value | | 2021 | 19.000743494424 | | 2020 | 19.17843866171 | | 2019 | 19.10780669145 | | 2018 | 19.092936802974 | | 2017 | 19.055762081784 | | 2016 | 19.011152416357 | | 2015 | 17.204460966543 | | 2014 | 17.124163568773 | | 2013 | 16.589591078067 | | 2012 | 38.14126394052 | | 2011 | 38.14126394052 | | 2010 | 38.066914498141 | | 2009 | 38.2156133829 | | 2008 | 38.14126394052 | | 2007 | 38.2156133829 | | 2006 | 38.289962825279 |
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