| Year | Value | | 2021 | 35.180749081616 | | 2020 | 35.148514851485 | | 2019 | 35.132545512616 | | 2018 | 35.095002395018 | | 2017 | 35.056911607414 | | 2016 | 34.960569585901 | | 2015 | 34.908220271349 | | 2014 | 34.853950518755 | | 2013 | 34.78579976067 | | 2012 | 34.732105817404 | | 2011 | 34.677856846539 | | 2010 | 34.623055444755 | | 2009 | 34.383725568409 | | 2008 | 34.144395692062 | | 2007 | 33.902361199745 | | 2006 | 33.663050414805 | | 2005 | 33.423739629866 | | 2004 | 33.184428844927 | | 2003 | 32.945118059987 | | 2002 | 32.705807275048 | | 2001 | 32.466496490108 | | 2000 | 32.227185705169 | | 1999 | 32.107530312699 | | 1998 | 31.98787492023 | | 1997 | 31.86821952776 | | 1996 | 31.74856413529 | | 1995 | 31.628908742821 | | 1994 | 31.509253350351 | | 1993 | 31.389597957881 | | 1992 | 31.269942565412 |
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