| Year | Value | | 2020 | 0.50853744630443 | | 2019 | 0.50732650347515 | | 2018 | 0.51320886408312 | | 2017 | 0.51934780608011 | | 2016 | 0.52657402267861 | | 2015 | 0.53366985926812 | | 2014 | 0.54055231409651 | | 2013 | 0.54819748233857 | | 2012 | 0.55619313283062 | | 2011 | 0.56501367208451 | | 2010 | 0.74482449708936 | | 2009 | 0.76898212487792 | | 2008 | 0.78356989038127 | | 2007 | 0.7974137397687 | | 2006 | 0.81050639880828 | | 2005 | 0.86269113941307 | | 2004 | 0.72392131380715 | | 2003 | 0.70746263025173 | | 2002 | 0.72351061822174 | | 2001 | 0.74092383735158 | | 2000 | 0.83343922542202 | | 1999 | 1.0147873955633 | | 1998 | 1.1001108581712 | | 1997 | 0.96799657014052 | | 1996 | 0.52947287752164 | | 1995 | 0.49227744189975 | | 1994 | 0.24234354936605 | | 1993 | 0.51315876756787 | | 1992 | 0.51612437048956 |
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