| Year | Value | | 2021 | 46.466128745118 | | 2020 | 46.589868582818 | | 2019 | 46.709586192084 | | 2018 | 46.833504975928 | | 2017 | 46.950119848874 | | 2016 | 47.124002657104 | | 2015 | 47.27608910015 | | 2014 | 47.423885971927 | | 2013 | 47.571157285622 | | 2012 | 47.718952524582 | | 2011 | 47.866747763542 | | 2010 | 48.014543002502 | | 2009 | 48.295098051425 | | 2008 | 48.575653100348 | | 2007 | 48.856208149272 | | 2006 | 49.136763198195 | | 2005 | 49.417318247118 | | 2004 | 49.697873296042 | | 2003 | 49.978428344965 | | 2002 | 50.258983393888 | | 2001 | 50.539538442811 | | 2000 | 50.820093491735 | | 1999 | 51.096293232696 | | 1998 | 51.372492973657 | | 1997 | 51.574931481681 | | 1996 | 51.850736772514 | | 1995 | 52.126542063348 | | 1994 | 52.402347354182 | | 1993 | 52.678152645016 | | 1992 | 52.95395793585 | | 1991 | 53.229763226683 | | 1990 | 53.505568517517 |
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