| Year | Value | | 2022 | 23.090608814595 | | 2021 | 21.730796222543 | | 2020 | 21.405314850144 | | 2019 | 23.117332972792 | | 2018 | 22.430795033117 | | 2017 | 23.340104411996 | | 2016 | 23.503460207612 | | 2015 | 22.751436569913 | | 2014 | 22.476866726642 | | 2013 | 22.483046609147 | | 2012 | 23.656403683068 | | 2011 | 23.213115268832 | | 2010 | 21.427393041757 | | 2009 | 23.509396197042 | | 2008 | 24.224504453497 | | 2007 | 20.955289576198 | | 2006 | 18.570112908723 | | 2005 | 16.542608575928 | | 2004 | 15.102348258909 | | 2003 | 10.922338599503 | | 2002 | 11.621512875536 | | 2001 | 11.804674857657 | | 2000 | 11.401433039334 | | 1999 | 11.191278423624 | | 1998 | 10.015730471317 | | 1997 | 10.623723901732 | | 1996 | 7.8764378958253 | | 1995 | 5.4148429603033 |
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