| Year | Value | | 2021 | 51.20409155 | | 2020 | 40.31067242 | | 2019 | 30.23161545 | | 2018 | 30.081 | | 2017 | 29.9312292 | | 2016 | 28 | | 2015 | 25.82 | | 2014 | 24.41 | | 2013 | 23 | | 2012 | 21.5724 | | 2011 | 20.1612 | | 2010 | 18.75 | | 2009 | 16.41 | | 2008 | 15.48 | | 2007 | 14.5904832 | | 2006 | 14.18201978 | | 2005 | 13.75948422 | | 2004 | 13.32285269 | | 2003 | 10.16184431 | | 2002 | 7.580665169 | | 2001 | 6.310917888 | | 2000 | 4.638516816 | | 1999 | 0.363203161 | | 1998 | 0.295847047 |
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