| Year | Value | | 2021 | 12.559104360389 | | 2020 | 11.795125412427 | | 2019 | 11.759837449852 | | 2018 | 11.665992746561 | | 2017 | 11.756370693715 | | 2016 | 11.460370907689 | | 2015 | 11.175732798572 | | 2014 | 10.117257545497 | | 2013 | 10.635929243321 | | 2012 | 10.619351578358 | | 2011 | 7.5714812610071 | | 2010 | 10.213762113664 | | 2009 | 10.501265836938 | | 2008 | 10.744266813672 | | 2007 | 10.66575675223 | | 2006 | 10.329916076625 | | 2005 | 9.8724391176095 | | 2004 | 10.012888580663 | | 2003 | 9.6568945061175 | | 2002 | 10.054846206363 | | 2001 | 9.5362259451806 | | 1995 | 18.819074586303 | | 1990 | 18.010907430171 |
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