| Year | Value | | 2022 | 47.60650856197 | | 2021 | 47.618189382701 | | 2020 | 47.633213623783 | | 2019 | 47.650248391099 | | 2018 | 47.675525011225 | | 2017 | 47.707931537308 | | 2016 | 47.738440543252 | | 2015 | 47.761907834069 | | 2014 | 47.777479311625 | | 2013 | 47.78724665928 | | 2012 | 47.793684081367 | | 2011 | 47.798438707005 | | 2010 | 47.802727299194 | | 2009 | 47.806700433479 | | 2008 | 47.811415074144 | | 2007 | 47.817262729746 | | 2006 | 47.853950228323 | | 2005 | 47.9203162335 | | 2004 | 47.98170206879 | | 2003 | 48.036328768151 | | 2002 | 48.084025435536 | | 2001 | 48.125305293253 | | 2000 | 48.16339127986 | | 1999 | 48.200005671985 | | 1998 | 48.236312045217 | | 1997 | 48.274786149681 | | 1996 | 48.317687687377 | | 1995 | 48.364695352193 | | 1994 | 48.41292118549 | | 1993 | 48.461468655495 | | 1992 | 48.492725233898 | | 1991 | 48.508369238995 | | 1990 | 48.531006698305 | | 1989 | 48.579321074025 | | 1988 | 48.623521402434 | | 1987 | 48.649392169245 | | 1986 | 48.690791077793 | | 1985 | 48.745139444102 | | 1984 | 48.82183354631 | | 1983 | 48.940780607632 | | 1982 | 49.083785226822 | | 1981 | 49.273329460102 | | 1980 | 49.473673938654 | | 1979 | 49.612918084899 | | 1978 | 49.713057934597 | | 1977 | 49.788462844096 | | 1976 | 49.843168406173 | | 1975 | 49.882001623351 | | 1974 | 49.910606019153 | | 1973 | 49.935319108249 | | 1972 | 49.962283862838 | | 1971 | 49.991666689141 | | 1970 | 50.023514198321 | | 1969 | 50.016397816117 | | 1968 | 49.961823869361 | | 1967 | 49.898572442528 | | 1966 | 49.825375424469 | | 1965 | 49.746281340561 | | 1964 | 49.665155710349 | | 1963 | 49.582952583598 | | 1962 | 49.504071214686 | | 1961 | 49.459616579267 | | 1960 | 49.449489030978 |
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