| Year | Value | | 2020 | 0.93875603180458 | | 2019 | 0.85280177227321 | | 2018 | 0.87632381052215 | | 2017 | 0.89996363121655 | | 2016 | 0.93702092581226 | | 2015 | 0.94673302506188 | | 2014 | 0.94704337254852 | | 2013 | 1.1553603424488 | | 2012 | 1.1622048794082 | | 2011 | 1.1748259039566 | | 2010 | 1.1811692098716 | | 2009 | 1.2061520539356 | | 2008 | 1.2208804823846 | | 2007 | 1.2821791346716 | | 2006 | 1.3355818776109 | | 2005 | 1.1194408442894 | | 2004 | 1.154311356593 | | 2003 | 1.3445485393417 | | 2002 | 1.4703840281383 | | 2001 | 1.4435530391155 | | 2000 | 1.682799746307 | | 1999 | 1.6629844056007 | | 1998 | 1.8288331125821 | | 1997 | 1.9102166195057 | | 1996 | 1.9103444560245 | | 1995 | 1.8395370581266 | | 1994 | 1.2339600344583 | | 1993 | 1.2877350935752 | | 1992 | 1.3438129949836 | | 1991 | 1.5104469510769 |
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