| Year | Value | | 2021 | 10.889408099689 | | 2020 | 10.889408099689 | | 2019 | 10.889408099689 | | 2018 | 10.889408099689 | | 2017 | 10.889408099689 | | 2016 | 10.889408099689 | | 2015 | 10.889408099689 | | 2014 | 10.221962616822 | | 2013 | 9.5545171339564 | | 2012 | 8.8870716510903 | | 2011 | 8.2196261682243 | | 2010 | 7.5521806853583 | | 2009 | 7.5521806853583 | | 2008 | 7.5521806853583 | | 2007 | 7.5521806853583 | | 2006 | 7.5521806853583 | | 2005 | 7.5521806853583 | | 2004 | 7.5521806853583 | | 2003 | 7.5521806853583 | | 2002 | 7.5521806853583 | | 2001 | 7.5521806853583 | | 2000 | 7.5521806853583 | | 1999 | 7.8735981308411 | | 1998 | 8.195015576324 | | 1997 | 8.5164330218069 | | 1996 | 8.8378504672897 | | 1995 | 9.1592679127726 | | 1994 | 9.4806853582554 | | 1993 | 9.8021028037383 | | 1992 | 10.123520249221 | | 1991 | 10.444937694704 | | 1990 | 10.766355140187 |
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