| Year | Value | | 2022 | 28.882822061462 | | 2021 | 29.104478119476 | | 2020 | 27.112805768719 | | 2019 | 31.832004860026 | | 2018 | 32.715988446827 | | 2017 | 31.889888448604 | | 2016 | 30.272799713101 | | 2015 | 28.678899368355 | | 2014 | 29.878234964167 | | 2013 | 27.375850048638 | | 2012 | 26.661103152445 | | 2011 | 25.87093835912 | | 2010 | 23.799436782998 | | 2009 | 20.418408522201 | | 2008 | 16.199442583114 | | 2007 | 17.639744762369 | | 2006 | 21.899398678528 | | 2005 | 18.552264131027 | | 2004 | 14.572951248265 | | 2003 | 15.712922751483 | | 2002 | 13.064202337796 | | 2001 | 12.645071334326 | | 2000 | 21.899759227616 | | 1999 | 7.2487870782677 | | 1998 | 3.8801871756746 | | 1997 | 6.0495320576706 | | 1996 | 12.198955639221 |
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