| Year | Value | | 2020 | 0.6758745620156 | | 2019 | 0.68550377574118 | | 2018 | 0.71179904012085 | | 2017 | 0.71184443616122 | | 2016 | 0.71637605038619 | | 2015 | 0.72876892990105 | | 2014 | 0.72259887743722 | | 2013 | 0.74800237857891 | | 2012 | 0.7652769836395 | | 2011 | 0.78366129282878 | | 2010 | 0.81515805499907 | | 2009 | 0.82343523273712 | | 2008 | 0.84699459024424 | | 2007 | 0.86830617052654 | | 2006 | 1.0240769048978 | | 2005 | 0.91621687322809 | | 2004 | 0.9223041527726 | | 2003 | 0.94693076233972 | | 2002 | 0.97853563330594 | | 2001 | 1.0082234650692 | | 2000 | 0.99022057414738 | | 1999 | 0.99645500710422 | | 1998 | 1.0186356274719 | | 1997 | 1.03620496495 | | 1996 | 1.0250744205507 | | 1995 | 1.0759425952264 | | 1994 | 0.76114614170705 | | 1993 | 0.81884391424364 | | 1992 | 0.82558179110011 | | 1991 | 0.88284016887777 |
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