| Year | Value | | 2014 | 0.99 | | 2013 | 0.99 | | 2012 | 1.05 | | 2011 | 1.07 | | 2010 | 1.06 | | 2009 | 1.06 | | 2008 | 1.04 | | 2007 | 1.05 | | 2006 | 1.07 | | 2002 | 0.5 | | 2001 | 1 | | 1993 | 1.0710999966 | | 1992 | 1.3701000214 | | 1991 | 1.2745000124 | | 1990 | 1.3918999434 | | 1986 | 1.7142000198364 | | 1985 | 1.7556999921799 | | 1984 | 1.7152999639511 | | 1983 | 1.7146999835968 | | 1982 | 1.7135000228882 | | 1980 | 1.708899974823 | | 1976 | 1.7094000577927 | | 1975 | 1.7094999551773 | | 1970 | 1.1898000240326 | | 1960 | 0.83895766735077 |
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