| Year | Value | | 2020 | 0.50229829374851 | | 2019 | 0.46112980121432 | | 2018 | 0.41003686184384 | | 2017 | 0.42702884654124 | | 2016 | 0.43328527353001 | | 2015 | 0.47179761483234 | | 2014 | 0.46791675911796 | | 2013 | 0.45447482322627 | | 2012 | 0.50912145810863 | | 2011 | 0.51218100457555 | | 2010 | 0.54433025106639 | | 2009 | 0.50499496165684 | | 2008 | 0.51805408906808 | | 2007 | 0.52038121200253 | | 2006 | 0.50086263957693 | | 2005 | 0.54161226364911 | | 2004 | 0.52641912359795 | | 2003 | 1.2207231204959 | | 2002 | 1.0706162934563 | | 2001 | 1.1507873562682 | | 2000 | 1.2233808371017 | | 1999 | 1.1432096416306 | | 1998 | 1.2451914823514 | | 1997 | 1.2994874458507 | | 1996 | 1.4627715922791 | | 1995 | 1.7808473736373 | | 1994 | 1.7496506530863 | | 1993 | 2.1021817503119 |
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