| Year | Value | | 2021 | 45.279712187835 | | 2020 | 45.109507479329 | | 2019 | 44.939302770823 | | 2018 | 44.047195197682 | | 2017 | 43.879735044504 | | 2016 | 43.712274891327 | | 2015 | 43.544814738149 | | 2014 | 43.418422686814 | | 2013 | 43.292030635479 | | 2012 | 43.165638584144 | | 2011 | 43.039246532809 | | 2010 | 42.912854481474 | | 2009 | 42.704512523287 | | 2008 | 42.4961705651 | | 2007 | 42.287828606914 | | 2006 | 42.079486648727 | | 2005 | 41.87114469054 | | 2004 | 41.662802732353 | | 2003 | 41.454460774167 | | 2002 | 41.24611881598 | | 2001 | 41.037776857793 | | 2000 | 40.829434899607 | | 1999 | 40.047857586421 | | 1998 | 39.266280273235 | | 1997 | 38.48470296005 | | 1996 | 37.703125646864 | | 1995 | 36.921548333678 | | 1994 | 36.139971020493 | | 1993 | 35.358393707307 | | 1992 | 34.576816394121 | | 1991 | 33.795239080936 | | 1990 | 33.01366176775 |
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