Year | Value | 2017 | 3.85 | 2016 | 4.53 | 2015 | 4.1 | 2014 | 4.02 | 2013 | 4.51 | 2012 | 4.45 | 2011 | 4.85 | 2010 | 4.81 | 2009 | 4.42 | 2008 | 4.39 | 2007 | 4.58 | 2006 | 4.85 | 2005 | 4.68 | 2004 | 5.08 | 2003 | 5.24 | 2002 | 5.69 | 2001 | 6.44 | 2000 | 6.47 | 1999 | 6.67 | 1998 | 6.03 | 1997 | 6.26 | 1996 | 6.75 | 1995 | 7.2 | 1994 | 8.87 | 1993 | 7.42 | 1992 | 8.92 | 1991 | 10.3 | 1990 | 8.37 | 1989 | 6.62 | 1988 | 5.27 |
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