| Year | Value | | 2021 | 59.270527497745 | | 2020 | 59.417478051337 | | 2019 | 59.55852617927 | | 2018 | 59.708427951673 | | 2017 | 59.832881478415 | | 2016 | 60.071032550304 | | 2015 | 60.286714508252 | | 2014 | 60.470867920375 | | 2013 | 60.655021332497 | | 2012 | 60.83917474462 | | 2011 | 61.023328156743 | | 2010 | 61.207481568866 | | 2009 | 61.680169272111 | | 2008 | 62.152856975356 | | 2007 | 62.625544678601 | | 2006 | 63.098232381846 | | 2005 | 63.570920085091 | | 2004 | 64.043607788336 | | 2003 | 64.516295491581 | | 2002 | 64.988983194826 | | 2001 | 65.461670898071 | | 2000 | 65.934358601316 | | 1999 | 66.386724797622 | | 1998 | 66.839090993929 | | 1997 | 67.291457190236 | | 1996 | 67.743823386543 | | 1995 | 68.19618958285 | | 1994 | 68.648555779157 | | 1993 | 69.100921975463 | | 1992 | 69.55328817177 | | 1991 | 70.005654368077 | | 1990 | 70.458020564384 |
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