| Year | Value | | 2016 | 9.2316531130631 | | 2015 | 9.6742835759004 | | 2014 | 10.125874098749 | | 2013 | 8.9703476238005 | | 2012 | 8.9168203869488 | | 2011 | 8.0915091387519 | | 2010 | 8.5215217987364 | | 2009 | 8.0633936779691 | | 2008 | 9.0179286858664 | | 2007 | 8.9390470349367 | | 2006 | 8.4056002362416 | | 2005 | 8.8363568524586 | | 2004 | 10.931516107231 | | 2003 | 9.8939443030163 |
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