Year | Value | 2017 | 2.09 | 2016 | 2.11 | 2015 | 2.15 | 2014 | 2.22 | 2013 | 2.25 | 2012 | 2.27 | 2011 | 2.31 | 2010 | 2.37 | 2009 | 2.43 | 2008 | 2.44 | 2007 | 2.47 | 2006 | 2.48 | 2005 | 2.52 | 2003 | 2.42 | 2002 | 2.59 | 2001 | 2.78 | 2000 | 2.82 | 1996 | 3.1099998951 | 1993 | 3.5 | 1990 | 3.3452999592 | 1987 | 3.5603001117706 | 1975 | 4.9951000213623 | 1970 | 3.6918001174927 | 1960 | 3.2017953395844 |
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