| Year | Value | | 2020 | 0.49554515676786 | | 2019 | 0.4722104169618 | | 2018 | 0.4926028726185 | | 2017 | 0.4564917694534 | | 2016 | 0.48979723924912 | | 2015 | 0.4754615094422 | | 2014 | 0.5069558853748 | | 2013 | 0.50968653598455 | | 2012 | 0.52152944456885 | | 2011 | 0.53780092853354 | | 2010 | 0.59975216390897 | | 2009 | 0.60529943157943 | | 2008 | 0.8260571466334 | | 2007 | 0.83461466556275 | | 2006 | 0.97394810561006 | | 2005 | 0.9902173948024 | | 2004 | 0.98160818631024 | | 2003 | 0.861920143846 | | 2002 | 0.87081990714442 | | 2001 | 0.88811793179408 | | 2000 | 1.0379824696294 | | 1999 | 1.037917031219 | | 1998 | 1.1735508967734 | | 1997 | 1.1855231726789 | | 1996 | 1.448535330893 | | 1995 | 1.4373708169418 | | 1994 | 1.1684417893985 | | 1993 | 1.2213322781022 | | 1992 | 1.2047971737649 | | 1991 | 1.2326977562379 |
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