| Year | Value | | 2020 | 0.31051946801805 | | 2019 | 0.31668519275044 | | 2018 | 0.62207379759683 | | 2017 | 0.67469554363593 | | 2016 | 0.5230417317563 | | 2015 | 0.52622346956674 | | 2014 | 0.54269500181497 | | 2013 | 0.56324158587942 | | 2012 | 0.58378018936128 | | 2011 | 0.61217622567005 | | 2010 | 0.62782093816047 | | 2009 | 0.63572416634782 | | 2008 | 0.71873801731748 | | 2007 | 0.68976843488257 | | 2006 | 0.70367474589523 | | 2005 | 0.71817719787397 | | 2004 | 0.73793534280806 | | 2003 | 0.75499428720989 | | 2002 | 0.75686094446154 | | 2001 | 0.77879598141274 | | 2000 | 0.74137228009045 | | 1999 | 0.7661409480447 | | 1998 | 0.76817496314455 | | 1997 | 0.77903926128748 | | 1996 | 0.81455493300286 | | 1995 | 0.82709565361234 | | 1994 | 0.57643532395665 | | 1993 | 0.58219417340071 | | 1992 | 0.57932392897489 | | 1991 | 0.60479237477774 |
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