| Year | Value | | 2020 | 0.70843605656153 | | 2019 | 0.69529908290051 | | 2018 | 0.41769664267764 | | 2017 | 0.67978192595815 | | 2016 | 0.41026330833642 | | 2015 | 0.42238794601744 | | 2014 | 0.42541320873143 | | 2013 | 0.40990491549911 | | 2012 | 0.4154605823259 | | 2011 | 0.40903635059109 | | 2010 | 0.41105121293801 | | 2009 | 0.41288471040537 | | 2008 | 0.67990209409845 | | 2007 | 0.41598188773944 | | 2006 | 0.41831822358766 | | 2005 | 0.41102905503746 | | 2004 | 0.41314477676636 | | 2003 | 0.41148594432595 | | 2002 | 0.41859978372344 | | 2001 | 0.41495497738495 | | 2000 | 0.42246083436015 | | 1999 | 0.43683132581888 | | 1998 | 0.43917119036991 | | 1997 | 0.43363253978579 | | 1996 | 0.44069365180795 | | 1995 | 0.4349591138433 |
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