| Year | Value | | 2020 | 0.78823198764581 | | 2019 | 0.77717884791508 | | 2018 | 0.78221990561888 | | 2017 | 0.7772252387662 | | 2016 | 0.77657488168408 | | 2015 | 0.78454071069252 | | 2014 | 0.81029149302068 | | 2013 | 0.84048218898045 | | 2012 | 0.87653026591167 | | 2011 | 0.89801103297556 | | 2010 | 0.92723697606821 | | 2009 | 0.92510889408214 | | 2008 | 0.91183639763137 | | 2007 | 0.93106837312387 | | 2006 | 0.90714009855421 | | 2005 | 0.95193943884918 | | 2004 | 0.92021566303014 | | 2003 | 0.92672219004604 | | 2002 | 0.92510530017434 | | 2001 | 0.90776912446785 | | 2000 | 0.93756565475371 | | 1999 | 1.0271492862313 | | 1998 | 1.0534033426986 | | 1997 | 1.0288369940776 | | 1996 | 1.0773215785999 | | 1995 | 1.1325955628913 | | 1994 | 1.2039695607519 | | 1993 | 1.2927538270661 | | 1992 | 1.3790770005715 | | 1991 | 1.5417771927318 |
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