| Year | Value | | 2021 | 55.497150372644 | | 2020 | 55.986409469531 | | 2019 | 56.475668566418 | | 2018 | 56.964927663306 | | 2017 | 57.453748355984 | | 2016 | 57.943007452871 | | 2015 | 58.43182814555 | | 2014 | 58.945287154757 | | 2013 | 59.458746163963 | | 2012 | 59.97220517317 | | 2011 | 60.485664182376 | | 2010 | 60.999123191583 | | 2009 | 61.296843489698 | | 2008 | 61.594563787812 | | 2007 | 61.892284085927 | | 2006 | 62.190004384042 | | 2005 | 62.487724682157 | | 2004 | 62.785444980272 | | 2003 | 63.083165278387 | | 2002 | 63.380885576501 | | 2001 | 63.678605874616 | | 2000 | 63.976326172731 | | 1999 | 64.593292415607 | | 1998 | 65.210258658483 | | 1997 | 65.827224901359 | | 1996 | 66.444191144235 | | 1995 | 67.061157387111 | | 1994 | 67.678123629987 | | 1993 | 68.295089872863 | | 1992 | 68.912056115739 | | 1991 | 69.529022358615 | | 1990 | 70.145988601491 |
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