Year | Value | 2017 | 2.974 | 2016 | 2.256 | 2013 | 2.633 | 2012 | 2.6 | 2011 | 2.53 | 2010 | 2.497 | 2009 | 2.462 | 2008 | 2.44 | 2007 | 2.324 | 2006 | 2.245 | 2005 | 2.247 | 2004 | 2.262 | 2002 | 2.115 | 2001 | 1.999 | 2000 | 1.973 | 1998 | 1.864 | 1994 | 1.772 | 1993 | 1.77 | 1992 | 1.866 | 1991 | 1.816 | 1990 | 1.802 | 1989 | 1.811 | 1988 | 1.805 | 1987 | 1.79 | 1986 | 1.783 | 1985 | 1.762 | 1984 | 1.724 | 1983 | 1.972 | 1982 | 1.635 | 1981 | 1.541 | 1980 | 1.476 | 1979 | 1.413 | 1978 | 1.377 | 1977 | 1.355 | 1976 | 1.332 | 1975 | 1.318 | 1973 | 1.242 | 1971 | 1.208 | 1970 | 1.185 | 1965 | 1.316 | 1960 | 1.269 |
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