| Year | Value | | 2021 | 58.301202987385 | | 2020 | 58.283217973448 | | 2019 | 58.007059277502 | | 2018 | 57.923406727843 | | 2017 | 57.952554313781 | | 2016 | 57.980530696269 | | 2015 | 57.984566500227 | | 2014 | 58.610933272754 | | 2013 | 57.504893423193 | | 2012 | 57.907296925195 | | 2011 | 58.321420622337 | | 2010 | 58.725555871638 | | 2009 | 59.133606303548 | | 2008 | 59.545791309893 | | 2007 | 59.958622334765 | | 2006 | 60.392336813124 | | 2005 | 60.80775681486 | | 2004 | 61.222476385387 | | 2003 | 61.634360152061 | | 2002 | 62.044775194937 | | 2001 | 62.684814101961 | | 2000 | 62.683931049511 | | 1999 | 64.24776680771 | | 1998 | 64.254818993888 | | 1997 | 64.967089797837 | | 1996 | 64.974141984015 | | 1995 | 64.981194170193 | | 1994 | 64.974141984015 | | 1993 | 64.990597085096 | | 1992 | 65.171603196991 |
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