| Year | Value | | 2021 | 57.84150030248 | | 2020 | 57.838249885052 | | 2019 | 57.827812326082 | | 2018 | 57.825392600479 | | 2017 | 57.795601364593 | | 2016 | 57.73557517842 | | 2015 | 57.70175290033 | | 2014 | 57.700543169253 | | 2013 | 57.704545179593 | | 2012 | 57.68709622783 | | 2011 | 57.691935444845 | | 2010 | 57.670344560588 | | 2009 | 57.579095156254 | | 2008 | 57.568349328912 | | 2007 | 57.564535453654 | | 2006 | 57.55291213379 | | 2005 | 57.568352286475 | | 2004 | 57.515240952197 | | 2003 | 57.525528722838 | | 2002 | 57.431794524196 | | 2001 | 57.45000242119 | | 2000 | 57.386356758066 | | 1999 | 56.736593918143 | | 1998 | 56.348384922736 | | 1997 | 55.141377362799 | | 1996 | 54.390328899143 | | 1995 | 53.944506531117 | | 1994 | 53.90725452732 | | 1993 | 53.553961330017 | | 1992 | 53.428986865664 |
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