| Year | Value | | 2020 | 0.51765032306557 | | 2019 | 0.52818472944001 | | 2018 | 0.5488210081112 | | 2017 | 0.44087361310805 | | 2016 | 0.45752356807754 | | 2015 | 0.46558285832456 | | 2014 | 0.46340994665384 | | 2013 | 0.45651383629022 | | 2012 | 0.454514528292 | | 2011 | 0.17560584014851 | | 2010 | 0.17754821138495 | | 2009 | 0.18085425214183 | | 2008 | 0.17580212650252 | | 2007 | 0.17930444220779 | | 2005 | 0.18594296013755 | | 2004 | 0.12681029623519 | | 2003 | 0.23321454507292 | | 2002 | 0.23592241010359 | | 2001 | 0.28592201681222 | | 2000 | 0.3767048510516 | | 1999 | 0.35926482919472 | | 1998 | 0.36621039564039 | | 1997 | 0.3806693080041 | | 1996 | 0.39171292143414 | | 1995 | 0.40202007045 | | 1994 | 0.33016921172101 | | 1993 | 0.34038178923389 | | 1992 | 0.3508107235822 | | 1991 | 0.36105612527203 |
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