| Year | Value | | 2021 | 72.310492 | | 2020 | 70.32030996 | | 2019 | 69.69687508 | | 2018 | 62.4 | | 2017 | 56.16739447 | | 2016 | 54 | | 2015 | 51.91911572 | | 2014 | 49 | | 2013 | 46.5 | | 2012 | 41 | | 2011 | 33.97 | | 2010 | 24 | | 2009 | 10 | | 2008 | 8.43 | | 2007 | 8.065375174 | | 2006 | 7.607139675 | | 2005 | 7.48854253 | | 2004 | 8.425118683 | | 2003 | 7.007691726 | | 2002 | 6.710322437 | | 2001 | 6.346619318 | | 2000 | 5.348559732 | | 1999 | 4.116249583 | | 1998 | 2.906220867 | | 1997 | 1.632093791 | | 1996 | 0.841882931 | | 1995 | 0.676740104 | | 1994 | 0.246905533 | | 1993 | 0.113747184 | | 1992 | 0.038869106 | | 1991 | 0.013283591 |
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