| Year | Value | | 2021 | 57.982014388489 | | 2020 | 58.154676258993 | | 2019 | 58.327338129496 | | 2018 | 58.5 | | 2017 | 58.672661870504 | | 2016 | 57.805653710247 | | 2015 | 57.975265017668 | | 2014 | 58.14628975265 | | 2013 | 58.317314487633 | | 2012 | 58.488339222615 | | 2011 | 58.659363957597 | | 2010 | 58.830388692579 | | 2009 | 59.000706713781 | | 2008 | 59.171024734982 | | 2007 | 59.341342756184 | | 2006 | 59.511660777385 | | 2005 | 59.681978798587 | | 2004 | 59.852296819788 | | 2003 | 60.022614840989 | | 2002 | 60.192932862191 | | 2001 | 60.363250883392 | | 2000 | 60.533568904594 | | 1999 | 60.703886925795 | | 1998 | 60.874204946996 | | 1997 | 61.044522968198 | | 1996 | 61.214840989399 | | 1995 | 61.385159010601 | | 1994 | 61.555477031802 | | 1993 | 61.725795053004 | | 1992 | 61.896113074205 | | 1991 | 62.066431095406 | | 1990 | 62.236749116608 |
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