| Year | Value | | 2021 | 0.045185594454769 | | 2020 | 0.045185594454769 | | 2019 | 0.045185594454769 | | 2018 | 0.045185594454769 | | 2017 | 0.045185594454769 | | 2016 | 0.045185594454769 | | 2015 | 0.048641317996886 | | 2014 | 0.052101059822191 | | 2013 | 0.055560801647496 | | 2012 | 0.059020543472801 | | 2011 | 0.062480285298106 | | 2010 | 0.065940027123412 | | 2009 | 0.065294088100859 | | 2008 | 0.064648149078306 | | 2007 | 0.064002210055754 | | 2006 | 0.063356271033201 | | 2005 | 0.062710332010648 | | 2004 | 0.062064392988096 | | 2003 | 0.061418453965543 | | 2002 | 0.060772514942991 | | 2001 | 0.060126575920438 | | 2000 | 0.059480636897885 | | 1999 | 0.05793359787031 | | 1998 | 0.056386558842734 | | 1997 | 0.054839519815159 | | 1996 | 0.053292480787584 | | 1995 | 0.051745441760008 | | 1994 | 0.050198402732433 | | 1993 | 0.048651363704857 | | 1992 | 0.047104324677282 | | 1991 | 0.045557285649706 | | 1990 | 0.044010246622131 |
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