| Year | Value | | 2022 | 50.102530370245 | | 2021 | 50.114500267381 | | 2020 | 50.126962888488 | | 2019 | 50.137910199398 | | 2018 | 50.146232991431 | | 2017 | 50.153311815698 | | 2016 | 50.160436807536 | | 2015 | 50.167056243248 | | 2014 | 50.17426925101 | | 2013 | 50.184595409722 | | 2012 | 50.194459345544 | | 2011 | 50.202200109736 | | 2010 | 50.209034969451 | | 2009 | 50.214759683767 | | 2008 | 50.220368449242 | | 2007 | 50.227368107878 | | 2006 | 50.234252194243 | | 2005 | 50.238793591225 | | 2004 | 50.244028006703 | | 2003 | 50.247513161302 | | 2002 | 50.24748526226 | | 2001 | 50.245693136278 | | 2000 | 50.243632523087 | | 1999 | 50.244058106076 | | 1998 | 50.248883117585 | | 1997 | 50.258723533134 | | 1996 | 50.274413313987 | | 1995 | 50.293853879023 | | 1994 | 50.31202830043 | | 1993 | 50.328392255052 | | 1992 | 50.344029338665 | | 1991 | 50.359690198493 | | 1990 | 50.376107844287 | | 1989 | 50.393360893993 | | 1988 | 50.411505026105 | | 1987 | 50.430282721275 | | 1986 | 50.447630186464 | | 1985 | 50.464208381135 | | 1984 | 50.48153188357 | | 1983 | 50.499605342375 | | 1982 | 50.518573031964 | | 1981 | 50.538224519431 | | 1980 | 50.558405178628 | | 1979 | 50.578840625294 | | 1978 | 50.59960888145 | | 1977 | 50.619952649997 | | 1976 | 50.638833959737 | | 1975 | 50.656215843341 | | 1974 | 50.67250316507 | | 1973 | 50.687646521457 | | 1972 | 50.702104213675 | | 1971 | 50.718585030211 | | 1970 | 50.736134532756 | | 1969 | 50.754504734956 | | 1968 | 50.775596568582 | | 1967 | 50.796659873246 | | 1966 | 50.817903124437 | | 1965 | 50.841205697892 | | 1964 | 50.865307146115 | | 1963 | 50.891151610101 | | 1962 | 50.91969724788 | | 1961 | 50.95025410858 | | 1960 | 50.983336033723 |
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