| Year | Value | | 2021 | 17.365475091258 | | 2020 | 16.635261679629 | | 2019 | 19.581910527538 | | 2018 | 17.868642007684 | | 2017 | 19.237442700287 | | 2016 | 22.43146756699 | | 2015 | 22.432829253185 | | 2014 | 22.789099818312 | | 2013 | -8.3145786622912 | | 2012 | -9.9007702912035 | | 2011 | -12.449028690545 | | 2010 | -11.367633147007 | | 2009 | -12.234558709353 | | 2008 | -13.98421719647 | | 2007 | -19.902974473858 | | 2006 | -18.266880099931 | | 2005 | -18.75292344043 |
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