| Year | Value | | 2020 | 0.27507105204871 | | 2019 | 0.28446907094566 | | 2018 | 0.29679165638649 | | 2017 | 0.30982671324575 | | 2016 | 0.32760946410082 | | 2015 | 0.34243539908226 | | 2014 | 0.35926825347573 | | 2013 | 0.37257343637377 | | 2012 | 0.38540631007305 | | 2011 | 0.39861432122454 | | 2010 | 0.41222417314261 | | 2009 | 0.4262443762838 | | 2008 | 0.44244267896218 | | 2007 | 0.45712547248051 | | 2005 | 0.48653171519096 | | 2004 | 0.58648887451932 | | 2003 | 0.67906244990129 | | 2002 | 0.64468297714599 | | 2001 | 0.66527739256239 | | 2000 | 0.61042968579881 | | 1999 | 0.51605015460365 | | 1998 | 0.53249106505655 | | 1997 | 0.61226198808973 | | 1996 | 0.69445774177445 | | 1995 | 0.70802660200299 | | 1994 | 0.84066239152478 | | 1993 | 1.0106546096534 | | 1992 | 1.0438218792522 | | 1991 | 0.92415306377534 |
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