Year | Value | 2021 | 49.963219218601 | 2020 | 49.969392216878 | 2019 | 49.438514365081 | 2018 | 49.649425139536 | 2017 | 49.870624244451 | 2016 | 50.586692044548 | 2015 | 50.762622495434 | 2014 | 50.797602819002 | 2013 | 51.17724221302 | 2012 | 51.705033565678 | 2011 | 52.121710949356 | 2010 | 52.371202963039 | 2009 | 52.821317420716 | 2008 | 53.167519740734 | 2007 | 54.888243010365 | 2006 | 54.821368862368 | 2005 | 54.821368862368 | 2004 | 54.821368862368 | 2003 | 54.811080531907 | 2002 | 54.811080531907 | 2001 | 54.811080531907 | 2000 | 54.697908896834 | 1999 | 54.695851230742 | 1998 | 54.695336814218 | 1997 | 54.687620566373 | 1996 | 54.687620566373 | 1995 | 54.628462666221 | 1994 | 54.625890583606 | 1993 | 54.620746418375 | 1992 | 54.619203168806 | 1991 | 54.607371588775 | 1990 | 54.091411816147 | 1989 | 53.52503922426 | 1988 | 53.011137117724 | 1987 | 52.753414439672 | 1986 | 52.1829265156 | 1985 | 52.077213920111 | 1984 | 51.972015741146 | 1983 | 51.966357159392 | 1982 | 50.574860464518 | 1981 | 50.520846729597 | 1980 | 50.505414233905 | 1979 | 50.411790426708 | 1978 | 50.51467373132 | 1977 | 50.207567067054 | 1976 | 50.181846240901 | 1975 | 50.181846240901 | 1974 | 50.181846240901 | 1973 | 50.104169345919 | 1972 | 49.975565215155 | 1971 | 49.866508912266 | 1970 | 50.225057228838 | 1969 | 50.263124051545 | 1968 | 50.293989042928 | 1967 | 50.329998199542 | 1966 | 50.368579438772 | 1965 | 50.40201651277 | 1964 | 50.438025669385 | 1963 | 50.468890660768 | 1962 | 50.504899817382 | 1961 | 50.575374881041 |
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