| Year | Value | | 2022 | 50.41820066119 | | 2021 | 50.43394954504 | | 2020 | 50.452300689956 | | 2019 | 50.467201533104 | | 2018 | 50.47958648145 | | 2017 | 50.491026941454 | | 2016 | 50.502861862028 | | 2015 | 50.513534452167 | | 2014 | 50.51939922226 | | 2013 | 50.522751686682 | | 2012 | 50.526560343649 | | 2011 | 50.530051998262 | | 2010 | 50.533576824033 | | 2009 | 50.537886451271 | | 2008 | 50.543412125933 | | 2007 | 50.548043858023 | | 2006 | 50.55116097052 | | 2005 | 50.553852960269 | | 2004 | 50.555215319112 | | 2003 | 50.555163599641 | | 2002 | 50.554136467042 | | 2001 | 50.552287755596 | | 2000 | 50.548109126509 | | 1999 | 50.541769261656 | | 1998 | 50.535798007287 | | 1997 | 50.529377606764 | | 1996 | 50.523894123054 | | 1995 | 50.521007746423 | | 1994 | 50.517700685199 | | 1993 | 50.514355250125 | | 1992 | 50.511950906565 | | 1991 | 50.507123474417 | | 1990 | 50.499854034369 | | 1989 | 50.49197766911 | | 1988 | 50.485882719737 | | 1987 | 50.481199347119 | | 1986 | 50.476644352077 | | 1985 | 50.478646272644 | | 1984 | 50.485820473812 | | 1983 | 50.492309937483 | | 1982 | 50.497512469386 | | 1981 | 50.498810670325 | | 1980 | 50.495501067642 | | 1979 | 50.494791459337 | | 1978 | 50.497283281062 | | 1977 | 50.496912281016 | | 1976 | 50.496596459334 | | 1975 | 50.495528193911 | | 1974 | 50.488310011359 | | 1973 | 50.476385547134 | | 1972 | 50.46311329324 | | 1971 | 50.455576001899 | | 1970 | 50.45431485327 | | 1969 | 50.450589449991 | | 1968 | 50.444274737284 | | 1967 | 50.438877355373 | | 1966 | 50.433816658207 | | 1965 | 50.429037426245 | | 1964 | 50.424896235885 | | 1963 | 50.417667737983 | | 1962 | 50.410007418622 | | 1961 | 50.407993197048 | | 1960 | 50.412290516486 |
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