| Year | Value | | 2022 | 26.323497022995 | | 2021 | 29.662845469396 | | 2020 | 27.46986028513 | | 2019 | 27.822620220809 | | 2018 | 29.158156213865 | | 2017 | 28.016900801906 | | 2016 | 26.403455255769 | | 2015 | 28.908471945167 | | 2014 | 27.46920159719 | | 2013 | 28.43710946587 | | 2012 | 31.236503616489 | | 2011 | 32.722105620596 | | 2010 | 26.855278458201 | | 2009 | 26.040150244948 | | 2008 | 30.502074969875 | | 2007 | 29.13438648571 | | 2006 | 29.558257262165 | | 2005 | 27.955621433874 | | 2004 | 26.898870922831 | | 2003 | 22.877374051 | | 2002 | 20.635718420861 | | 2001 | 21.717559918944 | | 2000 | 24.41214460575 | | 1999 | 22.802271862062 | | 1998 | 22.866696954117 | | 1997 | 23.028450235804 | | 1996 | 20.170507561028 | | 1995 | 20.863108819387 | | 1994 | 20.109104704097 | | 1993 | 25.698680203046 |
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