| Year | Value | | 2020 | 0.19359622409925 | | 2019 | 0.18955836691676 | | 2018 | 0.28406809014166 | | 2017 | 0.2024607074382 | | 2016 | 0.303623590506 | | 2015 | 0.28649812473955 | | 2014 | 0.29735489306487 | | 2013 | 0.3092211141799 | | 2012 | 0.32206276320091 | | 2011 | 0.33595565385369 | | 2010 | 0.35140682527893 | | 2009 | 0.36837346371521 | | 2008 | 0.29309697992872 | | 2007 | 0.30832128310985 | | 2005 | 0.34270635206223 | | 2004 | 0.36225452727595 | | 2003 | 0.49775817376355 | | 2002 | 0.92982264643696 | | 2001 | 0.68161679503783 | | 2000 | 0.71655694388463 | | 1999 | 0.74904613656047 | | 1998 | 0.77859638536628 | | 1997 | 0.81766561514196 | | 1996 | 0.83671068113479 | | 1995 | 0.86624617633524 | | 1994 | 0.56008916619526 | | 1993 | 0.57898180260194 | | 1992 | 0.59826145221985 | | 1991 | 0.61788276292456 |
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