| Year | Value | | 2022 | 56.350663360515 | | 2021 | 56.135693328101 | | 2020 | 56.886279449579 | | 2019 | 58.335948436789 | | 2018 | 56.633659698242 | | 2017 | 56.764327122491 | | 2016 | 56.925687728355 | | 2015 | 55.601973784507 | | 2014 | 55.172918059328 | | 2013 | 55.186865667991 | | 2012 | 54.113107603438 | | 2011 | 53.051897289465 | | 2010 | 52.49431009606 | | 2009 | 52.642760921236 | | 2008 | 52.874987635513 | | 2007 | 55.102355340963 | | 2006 | 54.378329086986 | | 2005 | 53.762395028485 | | 2004 | 55.855052852067 | | 2003 | 54.968128911561 | | 2002 | 54.680278391789 | | 2001 | 55.476509603519 | | 2000 | 57.050643912459 | | 1999 | 57.483809927351 | | 1998 | 57.809029478149 | | 1997 | 57.84850135311 | | 1996 | 58.388426666198 | | 1995 | 58.310482021044 | | 1994 | 60.229660646653 | | 1993 | 57.722318347324 | | 1992 | 55.725961912324 | | 1991 | 57.441211135105 |
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