| Year | Value | | 2020 | 14.164539862387 | | 2019 | 14.501138371431 | | 2018 | 11.669737313173 | | 2017 | 15.882845103873 | | 2016 | 15.395970723955 | | 2015 | 14.095109388695 | | 2014 | 12.646640047158 | | 2013 | 13.032966596132 | | 2012 | 12.991313464602 | | 2011 | 12.545214028445 | | 2010 | 12.892850532025 | | 2009 | 12.973582842019 | | 2008 | 11.837613970839 | | 2007 | 13.05597058987 | | 2006 | 13.316144825833 | | 2005 | 13.300258431538 | | 2004 | 13.68704433629 | | 2003 | 12.767953809971 | | 2002 | 11.173283903102 | | 2001 | 10.585476749792 | | 2000 | 10.785078029997 |
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