| Year | Value | | 2020 | 2.8529713696815 | | 2019 | 2.074862009326 | | 2018 | 2.0731528208366 | | 2017 | 2.1215014168599 | | 2016 | 2.1198529077486 | | 2015 | 1.8869729077219 | | 2014 | 1.9107056576256 | | 2013 | 1.164114785951 | | 2012 | 1.1774522181862 | | 2011 | 1.1908254477233 | | 2010 | 1.2014675379855 | | 2009 | 1.2184153511473 | | 2008 | 1.2402828070306 | | 2007 | 1.2527403695584 | | 2006 | 1.2694639111606 | | 2005 | 1.520851161901 | | 2004 | 1.5393113476256 | | 2003 | 1.7531758175391 | | 2002 | 1.0827084043538 | | 2001 | 1.114107529839 | | 2000 | 0.94457064052964 | | 1999 | 1.2634339603069 | | 1998 | 1.2697284050941 | | 1997 | 1.2206534564837 | | 1996 | 1.2695958594247 | | 1995 | 0.78762935022011 | | 1994 | 1.1187158931492 | | 1993 | 2.2112676723723 | | 1992 | 2.2806874643643 |
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