| Year | Value | | 2021 | 49.960348929421 | | 2020 | 50.039651070579 | | 2019 | 50.158604282316 | | 2018 | 50.118953211737 | | 2017 | 50.198255352894 | | 2016 | 50.158604282316 | | 2015 | 50.039651070579 | | 2014 | 50 | | 2013 | 49.960348929421 | | 2012 | 50.237906423473 | | 2011 | 44.329896907217 | | 2010 | 44.369547977795 | | 2009 | 40.166534496431 | | 2008 | 42.13238208482 | | 2007 | 42.647641696393 | | 2006 | 48.132127408573 | | 2005 | 48.289421942588 | | 2004 | 49.626425481714 | | 2003 | 51.16004718836 | | 2002 | 52.457727093984 | | 2001 | 48.83995281164 | | 2000 | 48.564687377114 | | 1999 | 50.412898151789 | | 1998 | 50.766810853323 | | 1997 | 50.452221785293 | | 1996 | 50.727487219819 | | 1995 | 50.609516319308 | | 1994 | 50.963429020842 | | 1993 | 51.002752654345 | | 1992 | 51.395988989383 |
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