| Year | Value | | 2019 | 0.35950656 | | 2018 | 0.54284 | | 2017 | 0.5664 | | 2016 | 0.41874 | | 2015 | 0.8 | | 2014 | 1.098 | | 2013 | 0.988 | | 2012 | 1.126 | | 2011 | 1.606 | | 2010 | 1.533 | | 2009 | 2.833 | | 2008 | 1.948 | | 2007 | 3.674 | | 2006 | 2.312 | | 2005 | 2.639 | | 2004 | 3.189 | | 2003 | 3.562 | | 2002 | 4.52 | | 2001 | 4.107 | | 2000 | 3.876 | | 1999 | 3.7000000477 | | 1998 | 3.4000000954 | | 1997 | 3.5999999046 | | 1996 | 3.5999999046 | | 1995 | 3.5999999046 | | 1994 | 3.4000000954 | | 1993 | 3.4000000954 | | 1992 | 1.7000000477 |
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