| Year | Value | | 2021 | 11.494765460048 | | 2020 | 11.408614117642 | | 2019 | 11.434560406969 | | 2018 | 11.440790414613 | | 2017 | 11.452853759901 | | 2016 | 11.417826842827 | | 2015 | 11.434508983038 | | 2014 | 11.458411814507 | | 2013 | 11.418813615295 | | 2012 | 11.412033183347 | | 2011 | 11.431448533058 | | 2010 | 11.304697751687 | | 2009 | 11.420342389329 | | 2008 | 11.385932431213 | | 2007 | 11.400071394837 | | 2006 | 11.545860685446 | | 2005 | 11.720472581178 | | 2004 | 11.794098680325 | | 2003 | 11.79109830438 | | 2002 | 11.911260183967 | | 2001 | 12.038581317792 | | 2000 | 12.088361819181 | | 1999 | 12.094000557116 | | 1998 | 12.107433644467 | | 1997 | 12.169097463262 | | 1996 | 12.162553776917 | | 1995 | 12.171705315412 | | 1994 | 12.228366083102 | | 1993 | 12.256216849661 | | 1992 | 12.219490596591 | | 1991 | 11.239809408889 | | 1990 | 11.255963125952 | | 1989 | 11.286194170045 | | 1988 | 11.318249482819 | | 1987 | 11.386667699492 | | 1986 | 11.485127631521 | | 1985 | 11.484334611356 | | 1984 | 11.500760421564 | | 1983 | 11.404534003231 | | 1982 | 11.419935328841 | | 1981 | 11.402564126006 | | 1980 | 11.377697578522 | | 1979 | 11.352968132308 | | 1978 | 11.330966356637 | | 1977 | 11.180950801555 | | 1976 | 11.15631380265 | | 1975 | 11.127374255377 | | 1974 | 11.169344591009 | | 1973 | 11.195308085537 | | 1972 | 11.29057238085 | | 1971 | 11.301995236044 | | 1970 | 11.451802023156 | | 1969 | 11.524518915234 | | 1968 | 11.318263321454 | | 1967 | 11.046941751092 | | 1966 | 11.079518961025 | | 1965 | 11.099180569905 | | 1964 | 11.106002757957 | | 1963 | 11.135219701878 | | 1962 | 11.056919728872 | | 1961 | 11.133383522682 |
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