| Year | Value | | 2022 | 50.005684418459 | | 2021 | 50.034197025703 | | 2020 | 50.059914836803 | | 2019 | 50.080833398236 | | 2018 | 50.101274933373 | | 2017 | 50.118906445178 | | 2016 | 50.135211785962 | | 2015 | 50.152168166559 | | 2014 | 50.167475591872 | | 2013 | 50.180745836146 | | 2012 | 50.192195107327 | | 2011 | 50.203101502032 | | 2010 | 50.214073140106 | | 2009 | 50.226894846451 | | 2008 | 50.241174822926 | | 2007 | 50.254627288757 | | 2006 | 50.268216963609 | | 2005 | 50.280927188316 | | 2004 | 50.291149360421 | | 2003 | 50.300720286682 | | 2002 | 50.309790635719 | | 2001 | 50.318092618662 | | 2000 | 50.326913019801 | | 1999 | 50.338311849758 | | 1998 | 50.349568916903 | | 1997 | 50.361245765053 | | 1996 | 50.372377697926 | | 1995 | 50.382075292147 | | 1994 | 50.391212535309 | | 1993 | 50.396990402223 | | 1992 | 50.400323425566 | | 1991 | 50.400597145039 | | 1990 | 50.399825473133 | | 1989 | 50.401152841457 | | 1988 | 50.401221271907 | | 1987 | 50.398328657472 | | 1986 | 50.394736518685 | | 1985 | 50.391760597201 | | 1984 | 50.388398486759 | | 1983 | 50.382836129359 | | 1982 | 50.378315652467 | | 1981 | 50.374274483 | | 1980 | 50.374331639401 | | 1979 | 50.379694354558 | | 1978 | 50.385004002257 | | 1977 | 50.39310217781 | | 1976 | 50.403498152748 | | 1975 | 50.415181002439 | | 1974 | 50.430538786873 | | 1973 | 50.447228083082 | | 1972 | 50.464448054688 | | 1971 | 50.484758219163 | | 1970 | 50.506467381259 | | 1969 | 50.530131209412 | | 1968 | 50.552372471507 | | 1967 | 50.570612322413 | | 1966 | 50.587476633594 | | 1965 | 50.606962094818 | | 1964 | 50.627635569606 | | 1963 | 50.644080961027 | | 1962 | 50.65903636189 | | 1961 | 50.674718401763 | | 1960 | 50.691078227619 |
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