Year | Value | 2021 | 31.177049022764 | 2020 | 31.176904586714 | 2019 | 31.213754551827 | 2018 | 31.252635742153 | 2017 | 31.289997007739 | 2016 | 31.340915960085 | 2015 | 31.368386454776 | 2014 | 31.403806923408 | 2013 | 31.43820022402 | 2012 | 31.472313842139 | 2011 | 31.536963472969 | 2010 | 31.571771763964 | 2009 | 31.61217852672 | 2008 | 31.65162673188 | 2007 | 31.687577330296 | 2006 | 31.72734466713 | 2005 | 31.766064919372 | 2004 | 31.806941260891 | 2003 | 31.883171370535 | 2002 | 31.925177733103 | 2001 | 31.964887692759 | 2000 | 32.004846325437 | 1999 | 32.082354396436 | 1998 | 32.144665678708 | 1997 | 32.198819060986 | 1996 | 32.276722386494 | 1995 | 32.337257837772 | 1994 | 32.397153254166 | 1993 | 32.45485213707 | 1992 | 32.511019139176 |
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