Year | Value | 2021 | 18.565903005058 | 2020 | 18.565903005058 | 2019 | 18.565903005058 | 2018 | 18.565903005058 | 2017 | 18.673316708229 | 2016 | 18.673316708229 | 2015 | 18.673316708229 | 2014 | 18.675311720698 | 2013 | 18.675311720698 | 2012 | 18.675311720698 | 2011 | 18.685286783042 | 2010 | 18.693266832918 | 2009 | 18.703241895262 | 2008 | 18.713216957606 | 2007 | 18.713216957606 | 2006 | 18.763092269327 | 2005 | 18.773067331671 | 2004 | 18.793017456359 | 2003 | 18.802992518703 | 2002 | 18.822942643391 | 2001 | 18.84289276808 | 2000 | 18.84289276808 | 1999 | 18.84289276808 | 1998 | 18.862842892768 | 1997 | 18.902743142145 | 1996 | 18.922693266833 | 1995 | 18.942643391521 | 1994 | 18.952618453865 | 1993 | 18.952618453865 | 1992 | 18.962593516209 | 1991 | 18.962593516209 | 1990 | 18.962593516209 | 1989 | 18.952618453865 | 1988 | 18.952618453865 | 1987 | 18.952618453865 | 1986 | 18.952618453865 | 1985 | 18.952618453865 | 1984 | 18.952618453865 | 1983 | 18.952618453865 | 1982 | 18.952618453865 | 1981 | 18.952618453865 | 1980 | 18.952618453865 | 1979 | 19.062344139651 | 1978 | 19.162094763092 | 1977 | 19.261845386534 | 1976 | 19.351620947631 | 1975 | 19.451371571072 | 1974 | 19.551122194514 | 1973 | 19.660847880299 | 1972 | 19.760598503741 | 1971 | 19.860349127182 | 1970 | 19.960099750623 | 1969 | 21.147132169576 | 1968 | 21.147132169576 | 1967 | 21.147132169576 | 1966 | 21.147132169576 | 1965 | 21.147132169576 | 1964 | 21.147132169576 | 1963 | 21.147132169576 | 1962 | 21.147132169576 | 1961 | 21.147132169576 |
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