| Year | Value | | 2021 | 51.113118085347 | | 2020 | 51.642582975841 | | 2019 | 52.172047866335 | | 2018 | 52.70151275683 | | 2017 | 53.230977647325 | | 2016 | 53.760442537819 | | 2015 | 54.289907428313 | | 2014 | 54.709869044931 | | 2013 | 55.129830661549 | | 2012 | 55.549792278167 | | 2011 | 55.969753894784 | | 2010 | 56.389715511402 | | 2009 | 56.809674870174 | | 2008 | 57.229634228946 | | 2007 | 57.649593587717 | | 2006 | 58.069552946489 | | 2005 | 58.489512305261 | | 2004 | 58.909471664033 | | 2003 | 59.329431022804 | | 2002 | 59.749390381576 | | 2001 | 60.169349740348 | | 2000 | 60.589309099119 | | 1999 | 61.009268457891 | | 1998 | 61.429227816663 | | 1997 | 61.849187175435 | | 1996 | 62.269146534206 | | 1995 | 62.689105892978 | | 1994 | 63.10906525175 | | 1993 | 63.529024610522 | | 1992 | 63.948983969293 | | 1991 | 64.368943328065 | | 1990 | 64.788902686837 |
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