| Year | Value | | 2019 | 49.265998840332 | | 2018 | 49.080001831055 | | 2017 | 48.904998779297 | | 2016 | 48.873001098633 | | 2015 | 48.945999145508 | | 2014 | 48.487998962402 | | 2013 | 47.665000915527 | | 2012 | 46.821998596191 | | 2011 | 46.457000732422 | | 2010 | 46.602001190185 | | 2009 | 47.296001434326 | | 2008 | 48.915000915527 | | 2007 | 48.921001434326 | | 2006 | 48.993999481201 | | 2005 | 48.995998382568 | | 2004 | 49.04999923706 | | 2003 | 49.335998535156 | | 2002 | 50.408000946045 | | 2001 | 49.492000579834 | | 2000 | 49.305000305176 | | 1999 | 48.965000152588 | | 1998 | 48.833999633789 | | 1997 | 48.707000732422 | | 1996 | 48.576000213623 | | 1995 | 48.451999664307 | | 1994 | 48.209999084473 | | 1993 | 48.016998291016 | | 1992 | 47.778999328613 | | 1991 | 47.623001098633 |
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