| Year | Value | | 2022 | 25.498877588093 | | 2021 | 28.613649659743 | | 2020 | 25.971076793207 | | 2019 | 24.041652424871 | | 2018 | 25.731077772992 | | 2017 | 26.650178779609 | | 2016 | 25.461641779627 | | 2015 | 24.858578910075 | | 2014 | 25.214231229906 | | 2013 | 25.549171708839 | | 2012 | 26.798411497555 | | 2011 | 29.701105135165 | | 2010 | 30.891865807468 | | 2009 | 31.730933272908 | | 2008 | 36.022957215331 | | 2007 | 34.416744492936 | | 2006 | 34.977612000715 | | 2005 | 32.940889877081 | | 2004 | 32.305789968109 | | 2003 | 33.165804594575 | | 2002 | 31.073403135108 | | 2001 | 31.625594152168 | | 2000 | 31.978051165993 | | 1999 | 31.416117162066 | | 1998 | 30.703003075178 |
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