Year | Value | 2021 | 20.128301163799 | 2020 | 20.062515794147 | 2019 | 21.075036073761 | 2018 | 20.906442979382 | 2017 | 21.135630706765 | 2016 | 20.974921981361 | 2015 | 20.495122067313 | 2014 | 19.598705028767 | 2013 | 19.92719786428 | 2012 | 19.418658021524 | 2011 | 18.872120653417 | 2010 | 19.457877756537 | 2009 | 19.39641301998 | 2008 | 20.288975089574 | 2007 | 20.51121332251 | 2006 | 20.670392513391 | 2005 | 20.361580050667 | 2004 | 20.324889961786 | 2003 | 21.102018178103 | 2002 | 21.648003117425 | 2001 | 21.25396548255 | 2000 | 22.174787280448 | 1999 | 22.677588572553 | 1998 | 23.529299587599 | 1997 | 21.56614165123 | 1996 | 22.306488556534 | 1995 | 22.624934829179 |
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