| Year | Value | | 2022 | 50.231666756048 | | 2021 | 40.429735330138 | | 2020 | 36.064818601643 | | 2019 | 36.456701152396 | | 2018 | 34.585225613762 | | 2017 | 30.510561447291 | | 2016 | 32.305311047857 | | 2015 | 41.670010227138 | | 2014 | 16.215241235125 | | 2013 | 11.849553499011 | | 2012 | 11.487031421735 | | 2011 | 15.150247067903 | | 2010 | 11.776067338068 | | 2009 | 13.995877008497 | | 2008 | 22.748690945682 | | 2007 | 16.9301757097 | | 2006 | 37.05355868689 | | 2005 | 22.704673111787 | | 2004 | 12.578779694764 | | 2003 | 17.648231715449 | | 2002 | 18.383634723666 |
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