Year | Value | 2021 | 31.706720749965 | 2020 | 31.765254441348 | 2019 | 31.816730672275 | 2018 | 31.870535187874 | 2017 | 31.921902401317 | 2016 | 31.989093920078 | 2015 | 32.034110492584 | 2014 | 32.094727318157 | 2013 | 32.153648659749 | 2012 | 32.212662304307 | 2011 | 32.313561859986 | 2010 | 32.372972539259 | 2009 | 32.434378178761 | 2008 | 32.494633257408 | 2007 | 32.555412058898 | 2006 | 32.616382661178 | 2005 | 32.677136909862 | 2004 | 32.739727902331 | 2003 | 32.851707754931 | 2002 | 32.915720015807 | 2001 | 32.976853783769 | 2000 | 33.038257069925 | 1999 | 33.145220439011 | 1998 | 33.235466552962 | 1997 | 33.314287231661 | 1996 | 33.402383710216 | 1995 | 33.490119070284 | 1994 | 33.576921445002 | 1993 | 33.660640382621 | 1992 | 33.747167933312 |
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