| Year | Value | | 2023 | 15.16587638855 | | 2022 | 16.509433746338 | | 2021 | 16.981132507324 | | 2020 | 13.207547187805 | | 2019 | 15.094339370727 | | 2018 | 20.283018112183 | | 2017 | 20.952381134033 | | 2016 | 24.761905670166 | | 2015 | 24.761905670166 | | 2014 | 22.380952835083 | | 2013 | 24.170616149902 | | 2012 | 21.800947189331 | | 2011 | 19.431280136108 | | 2010 | 13.744075775147 | | 2009 | 14.218009948731 | | 2008 | 12.98076915741 | | 2007 | 14.975845336914 | | 2006 | 18.357488632202 | | 2005 | 12.135922431946 | | 2004 | 13.592232704163 | | 2003 | 18.592964172363 | | 2002 | 10.582010269165 | | 2000 | 11.640212059021 | | 1998 | 21.276596069336 | | 1996 | 30.851064682007 |
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