| Year | Value | | 2022 | 47.135140213256 | | 2021 | 47.12635046979 | | 2020 | 47.108880236431 | | 2019 | 47.15056086883 | | 2018 | 47.211264415545 | | 2017 | 47.27567598327 | | 2016 | 47.342525316094 | | 2015 | 47.411684587126 | | 2014 | 47.484410294033 | | 2013 | 47.557348367029 | | 2012 | 47.626136007521 | | 2011 | 47.692717794803 | | 2010 | 47.695358826402 | | 2009 | 47.667620852316 | | 2008 | 47.679497122331 | | 2007 | 47.683056608842 | | 2006 | 47.686337677552 | | 2005 | 47.700644560397 | | 2004 | 47.747487705794 | | 2003 | 47.817175650748 | | 2002 | 47.885727982916 | | 2001 | 47.979402586806 | | 2000 | 48.072412206372 | | 1999 | 48.13795802779 | | 1998 | 48.209353328196 | | 1997 | 48.281169830682 | | 1996 | 48.356145409673 | | 1995 | 48.442569759896 | | 1994 | 48.551733369027 | | 1993 | 48.677446102819 | | 1992 | 48.796159106451 | | 1991 | 48.931686903218 | | 1990 | 49.048879961042 | | 1989 | 49.078890333767 | | 1988 | 49.033140583225 | | 1987 | 48.948021722265 | | 1986 | 48.86992084024 | | 1985 | 48.80889605757 | | 1984 | 48.754947486521 | | 1983 | 48.716297913101 | | 1982 | 48.683376639838 | | 1981 | 48.698374165522 | | 1980 | 48.754556988453 | | 1979 | 48.796890623488 | | 1978 | 48.84188020344 | | 1977 | 48.887985032132 | | 1976 | 48.938604088703 | | 1975 | 48.989541299514 | | 1974 | 49.032118344772 | | 1973 | 49.081108397204 | | 1972 | 49.107127686688 | | 1971 | 49.11928726877 | | 1970 | 49.138835312828 | | 1969 | 49.153885049722 | | 1968 | 49.165139311597 | | 1967 | 49.171734820739 | | 1966 | 49.172724359515 | | 1965 | 49.174917491749 | | 1964 | 49.173226993021 | | 1963 | 49.16224445411 | | 1962 | 49.156698775625 | | 1961 | 49.149809177402 | | 1960 | 49.139320246118 |
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