| Year | Value | | 2022 | 50.002710622761 | | 2021 | 50.020442321742 | | 2020 | 50.038934462495 | | 2019 | 50.052805271171 | | 2018 | 50.062073030343 | | 2017 | 50.070201556959 | | 2016 | 50.077241442344 | | 2015 | 50.084139921695 | | 2014 | 50.091840835961 | | 2013 | 50.100718136801 | | 2012 | 50.11132233355 | | 2011 | 50.124001199347 | | 2010 | 50.138273443358 | | 2009 | 50.153076003071 | | 2008 | 50.167569027453 | | 2007 | 50.180702141908 | | 2006 | 50.191876500821 | | 2005 | 50.201217955466 | | 2004 | 50.209307710546 | | 2003 | 50.216934330062 | | 2002 | 50.224608217264 | | 2001 | 50.232634569347 | | 2000 | 50.241577276578 | | 1999 | 50.251196009677 | | 1998 | 50.261283796453 | | 1997 | 50.272171915621 | | 1996 | 50.283878733124 | | 1995 | 50.296844665467 | | 1994 | 50.311585884793 | | 1993 | 50.32841815088 | | 1992 | 50.347481308591 | | 1991 | 50.368578650096 | | 1990 | 50.390821431137 | | 1989 | 50.419109998395 | | 1988 | 50.44673337533 | | 1987 | 50.467062302398 | | 1986 | 50.486034464343 | | 1985 | 50.503876762863 | | 1984 | 50.520749663458 | | 1983 | 50.536407212965 | | 1982 | 50.55151891455 | | 1981 | 50.566524153658 | | 1980 | 50.58132731592 | | 1979 | 50.595926172734 | | 1978 | 50.610315463985 | | 1977 | 50.623866656867 | | 1976 | 50.636833298015 | | 1975 | 50.64915302304 | | 1974 | 50.660978212265 | | 1973 | 50.672363322766 | | 1972 | 50.682808305764 | | 1971 | 50.692848053201 | | 1970 | 50.702221624231 | | 1969 | 50.710634241654 | | 1968 | 50.719878792533 | | 1967 | 50.731665938212 | | 1966 | 50.746337179425 | | 1965 | 50.764179478023 | | 1964 | 50.78464852638 | | 1963 | 50.806273094147 | | 1962 | 50.829272859652 | | 1961 | 50.853095021502 | | 1960 | 50.877160291715 |
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