| Year | Value | | 2020 | 0.02012685554513 | | 2019 | 0.020284210182552 | | 2018 | 0.010305321956808 | | 2016 | 0.0042798664596067 | | 2015 | 0.0026187202270605 | | 2014 | 0.0026717846185359 | | 2013 | 0.0027295953647831 | | 2012 | 0.001162196896144 | | 2011 | 0.0011862126034615 | | 2006 | 0.14564418693593 | | 2003 | 0.15577170921243 | | 2002 | 0.16020583729616 | | 2001 | 0.25797692629506 | | 2000 | 0.16935942831926 | | 1999 | 0.17220489523282 | | 1998 | 0.17503695591579 | | 1997 | 0.1845813493635 | | 1996 | 0.23866397271866 | | 1995 | 0.24234727880358 | | 1993 | 0.28610788842365 | | 1992 | 0.2905490214309 | | 1991 | 0.29487423798047 |
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