| Year | Value | | 2022 | 49.612907949927 | | 2021 | 49.654169211892 | | 2020 | 49.703283814858 | | 2019 | 49.73431735426 | | 2018 | 49.761984293417 | | 2017 | 49.79130509187 | | 2016 | 49.818806398724 | | 2015 | 49.841929739379 | | 2014 | 49.861472255711 | | 2013 | 49.879491191114 | | 2012 | 49.897562092757 | | 2011 | 49.914043284587 | | 2010 | 49.928882166177 | | 2009 | 49.944798388044 | | 2008 | 49.961792592082 | | 2007 | 49.97964930793 | | 2006 | 49.998481434875 | | 2005 | 50.018326330322 | | 2004 | 50.03866268447 | | 2003 | 50.059053235597 | | 2002 | 50.092045237752 | | 2001 | 50.142654805893 | | 2000 | 50.197613119138 | | 1999 | 50.251840679944 | | 1998 | 50.305263175067 | | 1997 | 50.357038001645 | | 1996 | 50.406689536863 | | 1995 | 50.455201353967 | | 1994 | 50.503926305434 | | 1993 | 50.537370673043 | | 1992 | 50.554936929164 | | 1991 | 50.571775946787 | | 1990 | 50.587229501594 | | 1989 | 50.601732447614 | | 1988 | 50.616650646549 | | 1987 | 50.633722962629 | | 1986 | 50.654370874644 | | 1985 | 50.678379165565 | | 1984 | 50.705083950298 | | 1983 | 50.73414624595 | | 1982 | 50.765536023568 | | 1981 | 50.799558514138 | | 1980 | 50.81752090175 | | 1979 | 50.818034415544 | | 1978 | 50.818274558668 | | 1977 | 50.817602728382 | | 1976 | 50.816135051207 | | 1975 | 50.814378979862 | | 1974 | 50.81275519608 | | 1973 | 50.811041260393 | | 1972 | 50.809501151071 | | 1971 | 50.808606836316 | | 1970 | 50.822119419557 | | 1969 | 50.851273770462 | | 1968 | 50.882742401833 | | 1967 | 50.91618815578 | | 1966 | 50.951284559167 | | 1965 | 50.987827807623 | | 1964 | 51.02555134046 | | 1963 | 51.063072104268 | | 1962 | 51.101327983639 | | 1961 | 51.142276664962 | | 1960 | 51.183952434125 |
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