Year | Value | 2017 | 1.43 | 2016 | 1.43 | 2015 | 1.56 | 2014 | 1.56 | 2010 | 1.73 | 2009 | 1.73 | 2008 | 2.08 | 2007 | 2.1 | 2006 | 2.2 | 2005 | 2.2 | 2004 | 2.17 | 2003 | 2.17 | 2002 | 2.1 | 2001 | 2.1 | 2000 | 2.1 | 1997 | 2.0999999046 | 1996 | 2.0999999046 | 1993 | 1.9292999506 | 1992 | 2.0004000664 | 1991 | 2.0241999626 | 1990 | 2.0708999634 | 1989 | 2.0199000835419 | 1988 | 2.1247000694275 | 1986 | 2.0857000350952 | 1981 | 2.0722000598908 | 1980 | 2.0262999534607 | 1975 | 2.036600112915 | 1970 | 2.1805000305176 | 1960 | 2.1469793319702 |
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