| Year | Value | | 2022 | 50.122340362561 | | 2021 | 50.144690052055 | | 2020 | 50.165498352324 | | 2019 | 50.190295703294 | | 2018 | 50.21884393311 | | 2017 | 50.247946356696 | | 2016 | 50.283251311526 | | 2015 | 50.320713186604 | | 2014 | 50.356975454504 | | 2013 | 50.395603491074 | | 2012 | 50.434872748089 | | 2011 | 50.474057505152 | | 2010 | 50.51322620283 | | 2009 | 50.54048757289 | | 2008 | 50.556744328451 | | 2007 | 50.574906253636 | | 2006 | 50.596180341644 | | 2005 | 50.620110680113 | | 2004 | 50.642951637557 | | 2003 | 50.663728805498 | | 2002 | 50.683932667505 | | 2001 | 50.70187762645 | | 2000 | 50.719050220714 | | 1999 | 50.738711210112 | | 1998 | 50.757917534429 | | 1997 | 50.772963825742 | | 1996 | 50.786584359823 | | 1995 | 50.796570886632 | | 1994 | 50.798740510245 | | 1993 | 50.796163743013 | | 1992 | 50.786423327688 | | 1991 | 50.7675388018 | | 1990 | 50.742788118221 | | 1989 | 50.713382369264 | | 1988 | 50.678485406787 | | 1987 | 50.633767222798 | | 1986 | 50.581889251421 | | 1985 | 50.531154539397 | | 1984 | 50.481542682967 | | 1983 | 50.432648847363 | | 1982 | 50.386748591452 | | 1981 | 50.339936254583 | | 1980 | 50.289723250071 | | 1979 | 50.241186314013 | | 1978 | 50.198172045424 | | 1977 | 50.159034318318 | | 1976 | 50.120093883718 | | 1975 | 50.086125322675 | | 1974 | 50.059841633068 | | 1973 | 50.038546807148 | | 1972 | 50.019513289223 | | 1971 | 49.999619026543 | | 1970 | 49.978897997356 | | 1969 | 49.955606781252 | | 1968 | 49.928729697648 | | 1967 | 49.897487880431 | | 1966 | 49.8597369465 | | 1965 | 49.81652526293 | | 1964 | 49.769321357029 | | 1963 | 49.715796002629 | | 1962 | 49.654510120628 | | 1961 | 49.586728105766 | | 1960 | 49.511866755474 |
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