| Year | Value | | 2020 | 0.76966867278488 | | 2019 | 0.77302860080821 | | 2018 | 0.78156349761287 | | 2017 | 0.78058796750887 | | 2016 | 0.79023224238351 | | 2015 | 0.79627750433946 | | 2014 | 0.79938178670552 | | 2013 | 0.80662974704417 | | 2012 | 0.84879360776706 | | 2011 | 0.85383364935989 | | 2010 | 0.86387095356335 | | 2009 | 0.86621027440137 | | 2008 | 0.85530900063395 | | 2007 | 0.85567286869331 | | 2006 | 0.93156142845229 | | 2005 | 0.92519868275808 | | 2004 | 0.90599060678876 | | 2003 | 0.94165732968628 | | 2002 | 0.95721556635254 | | 2001 | 0.96881449795894 | | 2000 | 1.0242201698829 | | 1999 | 1.0369508711233 | | 1998 | 1.0711228887909 | | 1997 | 1.0910204767593 | | 1996 | 1.1272644604463 | | 1995 | 1.1419537962031 | | 1994 | 0.82492039129135 | | 1993 | 0.8624206209453 | | 1992 | 0.92137143449972 | | 1991 | 0.88448956469688 |
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