| Year | Value | | 2021 | 46.389877843824 | | 2020 | 46.512813700192 | | 2019 | 46.631749526816 | | 2018 | 46.75486776273 | | 2017 | 46.870715587467 | | 2016 | 47.042864072147 | | 2015 | 47.190978491179 | | 2014 | 47.33549004598 | | 2013 | 47.478818097803 | | 2012 | 47.61736651986 | | 2011 | 47.761159189935 | | 2010 | 47.907649681766 | | 2009 | 48.183638826556 | | 2008 | 48.459627971346 | | 2007 | 48.735617116136 | | 2006 | 49.0116307163 | | 2005 | 49.287595405716 | | 2004 | 49.563658742965 | | 2003 | 49.839673169467 | | 2002 | 50.115687871416 | | 2001 | 50.389138284736 | | 2000 | 50.665114209948 | | 1999 | 50.937139523322 | | 1998 | 51.209164836696 | | 1997 | 51.408139141391 | | 1996 | 51.679778455073 | | 1995 | 51.951417768755 | | 1994 | 52.223057082436 | | 1993 | 52.494696396118 | | 1992 | 52.7663357098 | | 1991 | 53.037975023482 | | 1990 | 53.309614337164 |
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