| Year | Value | | 2021 | 40.429735330138 | | 2020 | 36.064818328741 | | 2019 | 36.456700878746 | | 2018 | 34.585225379333 | | 2017 | 30.510561145942 | | 2016 | 32.305311047857 | | 2015 | 41.670009902247 | | 2014 | 16.215240596585 | | 2013 | 11.849554214601 | | 2012 | 11.487032234222 | | 2011 | 15.150247941436 | | 2010 | 11.776066537802 | | 2009 | 13.995877885995 | | 2008 | 22.748690945682 | | 2007 | 16.930176789566 | | 2006 | 37.05355988535 | | 2005 | 22.704671957647 | | 2004 | 12.578780914054 | | 2003 | 17.648230188893 | | 2002 | 18.383636556765 |
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