| Year | Value | | 2022 | 47.945683422386 | | 2021 | 47.847412229783 | | 2020 | 47.635771853995 | | 2019 | 47.530425392238 | | 2018 | 47.547300439279 | | 2017 | 47.56624336587 | | 2016 | 47.591186534557 | | 2015 | 47.673636583416 | | 2014 | 47.844054640238 | | 2013 | 48.07941696518 | | 2012 | 48.341458142263 | | 2011 | 48.594814445428 | | 2010 | 48.819270994196 | | 2009 | 49.027638754974 | | 2008 | 49.238611442855 | | 2007 | 49.445008554614 | | 2006 | 49.645708349694 | | 2005 | 49.833205948159 | | 2004 | 50.001840103999 | | 2003 | 50.151454811893 | | 2002 | 50.284720879508 | | 2001 | 50.392551776279 | | 2000 | 50.48006270486 | | 1999 | 50.560777946314 | | 1998 | 50.632236114692 | | 1997 | 50.695877664373 | | 1996 | 50.752368913423 | | 1995 | 50.804554611043 | | 1994 | 50.835327276737 | | 1993 | 50.849463725139 | | 1992 | 50.851634466845 | | 1991 | 50.836890117367 | | 1990 | 50.817397368444 | | 1989 | 50.809087892412 | | 1988 | 50.824622631204 | | 1987 | 50.853351845259 | | 1986 | 50.875133230744 | | 1985 | 50.879062032815 | | 1984 | 50.871190045743 | | 1983 | 50.849052343444 | | 1982 | 50.820511302172 | | 1981 | 50.796647821086 | | 1980 | 50.76879873019 | | 1979 | 50.738757273979 | | 1978 | 50.712523600002 | | 1977 | 50.683381865691 | | 1976 | 50.66119550511 | | 1975 | 50.64398575251 | | 1974 | 50.620509557216 | | 1973 | 50.594943912187 | | 1972 | 50.568937697955 | | 1971 | 50.543105331013 | | 1970 | 50.516934859097 | | 1969 | 50.48778298403 | | 1968 | 50.4556025687 | | 1967 | 50.42283441561 | | 1966 | 50.386806715385 | | 1965 | 50.349129093504 | | 1964 | 50.311515621588 | | 1963 | 50.273182538316 | | 1962 | 50.234156323942 | | 1961 | 50.196360031274 | | 1960 | 50.159260365496 |
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