| Year | Value | | 2020 | 0.11652701995766 | | 2019 | 0.11840804819504 | | 2018 | 0.11751668888617 | | 2017 | 0.12434665547132 | | 2016 | 0.1235936832943 | | 2015 | 0.12679878390968 | | 2014 | 0.1293824766377 | | 2013 | 0.13199195445171 | | 2012 | 0.13464077926956 | | 2011 | 0.13734226241162 | | 2010 | 0.14012734592388 | | 2009 | 0.14315803862404 | | 2008 | 0.13235440235795 | | 2007 | 0.13566057104961 | | 2005 | 0.071435080768074 | | 2004 | 0.073397142712146 | | 2003 | 0.075501825580213 | | 2002 | 0.077770951216504 | | 2001 | 0.080206456000973 | | 2000 | 0.094462100329378 | | 1999 | 0.097224271358775 | | 1998 | 0.10017027694953 | | 1997 | 0.10330863998566 | | 1996 | 0.19284733234285 | | 1995 | 0.17511107925062 | | 1994 | 0.098472383841976 | | 1993 | 0.10122299063326 | | 1992 | 0.10403952788646 | | 1991 | 0.13723397004304 |
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