| Year | Value | | 2022 | 50.345653924126 | | 2021 | 50.360040628668 | | 2020 | 50.377219478833 | | 2019 | 50.391216825197 | | 2018 | 50.402830935422 | | 2017 | 50.41338547463 | | 2016 | 50.424136944178 | | 2015 | 50.433770513812 | | 2014 | 50.439018477496 | | 2013 | 50.441969883225 | | 2012 | 50.445233714897 | | 2011 | 50.448082930008 | | 2010 | 50.450953890899 | | 2009 | 50.454578460038 | | 2008 | 50.459385120909 | | 2007 | 50.463312525433 | | 2006 | 50.46583765784 | | 2005 | 50.467912242949 | | 2004 | 50.468606434893 | | 2003 | 50.467924153266 | | 2002 | 50.46647710192 | | 2001 | 50.46443263037 | | 2000 | 50.459903342275 | | 1999 | 50.45395091962 | | 1998 | 50.449485535982 | | 1997 | 50.444183869907 | | 1996 | 50.439462630723 | | 1995 | 50.437158602427 | | 1994 | 50.434678839464 | | 1993 | 50.432251604335 | | 1992 | 50.430265408749 | | 1991 | 50.425286498498 | | 1990 | 50.417849285666 | | 1989 | 50.410026007935 | | 1988 | 50.404234838896 | | 1987 | 50.399842931552 | | 1986 | 50.395211747684 | | 1985 | 50.396558586914 | | 1984 | 50.402896429662 | | 1983 | 50.408870726586 | | 1982 | 50.413439701049 | | 1981 | 50.414015741312 | | 1980 | 50.410088709825 | | 1979 | 50.408561810656 | | 1978 | 50.410315750727 | | 1977 | 50.409380371574 | | 1976 | 50.40846609975 | | 1975 | 50.406960176602 | | 1974 | 50.39961815308 | | 1973 | 50.388135127312 | | 1972 | 50.375821610546 | | 1971 | 50.368755999806 | | 1970 | 50.367257903533 | | 1969 | 50.363542159293 | | 1968 | 50.357458718439 | | 1967 | 50.352301734182 | | 1966 | 50.347477535487 | | 1965 | 50.34253352763 | | 1964 | 50.338008973304 | | 1963 | 50.330693922221 | | 1962 | 50.322795130365 | | 1961 | 50.320212379158 | | 1960 | 50.32392753358 |
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