Year | Value | 2022 | 51.506785729715 | 2021 | 51.504240278786 | 2020 | 51.49456776768 | 2019 | 51.493803927441 | 2018 | 51.509301600535 | 2017 | 51.521240449608 | 2016 | 51.52599891664 | 2015 | 51.53467803071 | 2014 | 51.547888191504 | 2013 | 51.560878661454 | 2012 | 51.580896924607 | 2011 | 51.608523252284 | 2010 | 51.639871221701 | 2009 | 51.676895137814 | 2008 | 51.71596081936 | 2007 | 51.752492377609 | 2006 | 51.782531010673 | 2005 | 51.803576635901 | 2004 | 51.816850079514 | 2003 | 51.825653763025 | 2002 | 51.832419831946 | 2001 | 51.831307577232 | 2000 | 51.817314343064 | 1999 | 51.79224583852 | 1998 | 51.748582592171 | 1997 | 51.693539798095 | 1996 | 51.635696343075 | 1995 | 51.566891915723 | 1994 | 51.489507006286 | 1993 | 51.411531161401 | 1992 | 51.339833466766 | 1991 | 51.279504131094 | 1990 | 51.222955234496 | 1989 | 51.16481135065 | 1988 | 51.109082750148 | 1987 | 51.053959871438 | 1986 | 50.999077833133 | 1985 | 50.944861297582 | 1984 | 50.893071081236 | 1983 | 50.84409161549 | 1982 | 50.801690209615 | 1981 | 50.767229216035 | 1980 | 50.73420435102 | 1979 | 50.703783093896 | 1978 | 50.67926642508 | 1977 | 50.657907400767 | 1976 | 50.639709815496 | 1975 | 50.624655018056 | 1974 | 50.612614811011 | 1973 | 50.602988134217 | 1972 | 50.594110241509 | 1971 | 50.585420748393 | 1970 | 50.580150181464 | 1969 | 50.577880513135 | 1968 | 50.576965374967 | 1967 | 50.580345899251 | 1966 | 50.589831456611 | 1965 | 50.606701797146 | 1964 | 50.6311721811 | 1963 | 50.667013806967 | 1962 | 50.710926761759 | 1961 | 50.758757749385 | 1960 | 50.809502980072 |
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