Year | Value | 2021 | 2.24 | 2020 | 1.71 | 2019 | 2.55 | 2018 | 2.46 | 2017 | 2.48 | 2016 | 2.48 | 2015 | 2.73 | 2014 | 2.76 | 2013 | 2.21 | 2012 | 2.28 | 2011 | 2.3 | 2010 | 2.78 | 2009 | 2.44 | 2008 | 2.37 | 2007 | 2.53 | 2006 | 2.75 | 2005 | 2.68 | 2004 | 2.64 | 2003 | 2.54 | 2002 | 2.57 | 2001 | 4.26 | 2000 | 3.3 | 1999 | 4.31 | 1998 | 3.9 | 1997 | 3.47 | 1996 | 4.22 | 1995 | 5.73 | 1994 | 4.21 | 1993 | 3.54 | 1992 | 3.88 | 1991 | 4.71 | 1990 | 6.01 | 1989 | 3.49 | 1988 | 3.14 |
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