| Year | Value | | 2020 | 0.7430171250587 | | 2019 | 0.71931889132818 | | 2018 | 0.58212739534643 | | 2017 | 0.57939525620134 | | 2016 | 0.58358105508573 | | 2015 | 0.5811475727403 | | 2014 | 0.57205975411318 | | 2013 | 0.58292840199894 | | 2012 | 0.5843152474539 | | 2011 | 0.60035309656198 | | 2010 | 0.59783760241077 | | 2009 | 0.58530331186885 | | 2008 | 0.57378107383128 | | 2007 | 0.57905472211888 | | 2006 | 0.43551667520763 | | 2005 | 0.44168505794172 | | 2004 | 0.30148450972589 | | 2003 | 0.42199170708149 | | 2002 | 0.4330858328 | | 2001 | 0.44226551328189 | | 2000 | 1.2397431913304 | | 1999 | 1.2683487790029 | | 1998 | 1.266756709103 | | 1997 | 1.2086687827129 | | 1996 | 1.2372930896284 | | 1995 | 1.26574151357 | | 1994 | 0.37868962030685 | | 1993 | 0.39168683853885 | | 1992 | 0.39766965581691 | | 1991 | 0.40641072274051 |
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