| Year | Value | | 2021 | 55.161493262169 | | 2020 | 55.647312586842 | | 2019 | 56.133128956132 | | 2018 | 56.618949736442 | | 2017 | 57.104770516751 | | 2016 | 57.590586886041 | | 2015 | 58.07640766635 | | 2014 | 58.562226682252 | | 2013 | 59.048045698154 | | 2012 | 59.533864714056 | | 2011 | 60.019683729957 | | 2010 | 60.505502745859 | | 2009 | 60.802364306037 | | 2008 | 61.099225866214 | | 2007 | 61.396087426391 | | 2006 | 61.692948986569 | | 2005 | 61.989810546746 | | 2004 | 62.286672106923 | | 2003 | 62.5835336671 | | 2002 | 62.880395227278 | | 2001 | 63.177256787455 | | 2000 | 63.474118347632 | | 1999 | 63.77097990781 | | 1998 | 64.067841467987 | | 1997 | 64.364703028164 | | 1996 | 64.661564588342 | | 1995 | 64.958426148519 | | 1994 | 65.255287708696 | | 1993 | 65.552149268874 | | 1992 | 65.849010829051 | | 1991 | 66.145872389228 | | 1990 | 66.442733949406 |
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