| Year | Value | | 2020 | 0.91738069464066 | | 2019 | 0.86953119225769 | | 2018 | 0.57081384882215 | | 2017 | 0.44450371160599 | | 2016 | 0.58503480957117 | | 2015 | 0.59166211541962 | | 2014 | 0.59907005893928 | | 2013 | 0.60723544386575 | | 2012 | 0.40200149449967 | | 2011 | 0.40832600748438 | | 2010 | 0.41996493781101 | | 2009 | 0.4273737880723 | | 2008 | 0.50479555779909 | | 2007 | 0.4419730499224 | | 2006 | 0.45070304434184 | | 2005 | 0.45879635310248 | | 2004 | 0.46672419313698 | | 2003 | 0.49655994306113 | | 2002 | 0.50408307289041 | | 2001 | 1.8202399303758 | | 2000 | 1.8492299690832 | | 1999 | 1.880384068446 | | 1998 | 1.8897035079116 | | 1997 | 1.9223515956735 | | 1996 | 1.978581851458 | | 1995 | 1.3219686000982 |
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