Year | Value | 2018 | 3.28 | 2017 | 2.97 | 2016 | 6.17 | 2015 | 6.07 | 2014 | 3.02 | 2013 | 6.5 | 2012 | 6.82 | 2011 | 7.49 | 2010 | 7.73 | 2009 | 5.28 | 2008 | 6.25 | 2007 | 6.4 | 2006 | 8.04 | 2005 | 9.2 | 2004 | 10.21 | 2003 | 18.32 | 2002 | 15.29 | 2001 | 18.08 | 2000 | 17.97 | 1999 | 15.96 | 1998 | 14.72 | 1997 | 14.76 | 1996 | 14.59 | 1995 | 12.36 | 1991 | 14.29 |
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