| Year | Value | | 2020 | 0.8237607936295 | | 2019 | 0.83506748025815 | | 2018 | 0.8349435445578 | | 2017 | 0.83798823940609 | | 2016 | 0.84756603208264 | | 2015 | 0.83682559033776 | | 2014 | 0.83376867673062 | | 2013 | 0.84687812477006 | | 2012 | 0.86945176098709 | | 2011 | 0.8721943850546 | | 2010 | 0.88390511882321 | | 2009 | 0.90107894601906 | | 2008 | 0.91035750062223 | | 2007 | 0.92720231649255 | | 2006 | 1.0025087184333 | | 2005 | 1.017162302929 | | 2004 | 0.96392416916767 | | 2003 | 1.0045835035806 | | 2002 | 1.0133294735641 | | 2001 | 1.014901564695 | | 2000 | 1.053136860953 | | 1999 | 1.0730501940741 | | 1998 | 1.1064554486833 | | 1997 | 1.1446209380821 | | 1996 | 1.1533916494182 | | 1995 | 1.1585976159417 | | 1994 | 0.82121213219294 | | 1993 | 0.87554515289091 | | 1992 | 0.9021253248445 | | 1991 | 0.92319851552801 |
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