| Year | Value | | 2020 | 0.87357318805876 | | 2019 | 0.89519067760364 | | 2018 | 0.6761048293849 | | 2017 | 0.74065405678447 | | 2016 | 0.8661736685813 | | 2015 | 0.88642405414549 | | 2014 | 0.90696971517737 | | 2013 | 0.81686133046436 | | 2012 | 0.84096455376635 | | 2011 | 0.86470590570562 | | 2010 | 0.88863933890333 | | 2009 | 0.91580526157966 | | 2008 | 0.94081216281964 | | 2007 | 0.96666043400844 | | 2005 | 1.0182327668468 | | 2004 | 1.0246794034316 | | 2003 | 1.0958955876031 | | 2002 | 1.1392217059274 | | 2001 | 1.1682368126483 | | 2000 | 1.1838737237858 | | 1999 | 1.2216389592407 | | 1998 | 1.2534194793975 | | 1997 | 1.2816090390028 | | 1996 | 1.3076780777995 | | 1995 | 1.3604156899455 | | 1994 | 1.6288535110955 | | 1993 | 1.2264170226683 | | 1992 | 1.5708574525405 | | 1991 | 2.1652192176197 |
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