| Year | Value | | 2021 | 38.527214514408 | | 2020 | 38.527214514408 | | 2019 | 38.527214514408 | | 2018 | 38.527214514408 | | 2017 | 38.527214514408 | | 2016 | 38.527214514408 | | 2015 | 38.527214514408 | | 2014 | 38.527214514408 | | 2013 | 38.527214514408 | | 2012 | 38.527214514408 | | 2011 | 38.527214514408 | | 2010 | 38.527214514408 | | 2009 | 38.527214514408 | | 2008 | 38.527214514408 | | 2007 | 38.527214514408 | | 2006 | 38.527214514408 | | 2005 | 38.527214514408 | | 2004 | 38.527214514408 | | 2003 | 38.527214514408 | | 2002 | 38.527214514408 | | 2001 | 38.527214514408 | | 2000 | 38.527214514408 | | 1999 | 38.527214514408 | | 1998 | 38.527214514408 | | 1997 | 38.527214514408 | | 1996 | 38.527214514408 | | 1995 | 38.527214514408 | | 1994 | 38.527214514408 | | 1993 | 38.50781022606 | | 1992 | 38.496167653051 | | 1991 | 38.484525080043 | | 1990 | 38.474822935869 | | 1989 | 38.454448433104 | | 1988 | 38.435044144756 | | 1987 | 38.415639856408 | | 1986 | 38.39623556806 | | 1985 | 38.376831279713 | | 1984 | 38.357426991365 | | 1983 | 38.346754632774 | | 1982 | 38.327350344426 | | 1981 | 38.307946056078 | | 1980 | 38.288541767731 | | 1979 | 38.27398855147 | | 1978 | 38.271077908218 | | 1977 | 38.274958765887 | | 1976 | 38.27398855147 | | 1975 | 38.271077908218 | | 1974 | 38.274958765887 | | 1973 | 38.304065198409 | | 1972 | 38.316677985835 | | 1971 | 38.316677985835 | | 1970 | 38.35548656253 | | 1969 | 38.35548656253 | | 1968 | 38.345784418357 | | 1967 | 38.345784418357 | | 1966 | 38.345784418357 | | 1965 | 38.345784418357 | | 1964 | 38.345784418357 | | 1963 | 38.345784418357 | | 1962 | 38.344814203939 | | 1961 | 38.344814203939 |
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