| Year | Value | | 2022 | 49.765432580476 | | 2021 | 49.783689322467 | | 2020 | 49.802664378123 | | 2019 | 49.817506385533 | | 2018 | 49.831547912474 | | 2017 | 49.845201629174 | | 2016 | 49.85800893307 | | 2015 | 49.870749036753 | | 2014 | 49.883118948938 | | 2013 | 49.894284775487 | | 2012 | 49.904884057439 | | 2011 | 49.915783908921 | | 2010 | 49.924777775249 | | 2009 | 49.932362675606 | | 2008 | 49.921963059491 | | 2007 | 49.910556463412 | | 2006 | 49.916721901892 | | 2005 | 49.925944700361 | | 2004 | 49.937961630595 | | 2003 | 49.951891656631 | | 2002 | 49.966581490668 | | 2001 | 49.981686337356 | | 2000 | 49.997617391871 | | 1999 | 50.014129149305 | | 1998 | 50.03291499485 | | 1997 | 50.05113475957 | | 1996 | 50.067570758962 | | 1995 | 50.081035096256 | | 1994 | 50.092237049063 | | 1993 | 50.102440151792 | | 1992 | 50.109386256735 | | 1991 | 50.114458923141 | | 1990 | 50.119015042387 | | 1989 | 50.122859493071 | | 1988 | 50.12747673102 | | 1987 | 50.131429067184 | | 1986 | 50.135378845182 | | 1985 | 50.137512465762 | | 1984 | 50.138056481337 | | 1983 | 50.138416433347 | | 1982 | 50.138184877775 | | 1981 | 50.136921330452 | | 1980 | 50.135805884823 | | 1979 | 50.136538912166 | | 1978 | 50.135966079987 | | 1977 | 50.135412911931 | | 1976 | 50.134859876137 | | 1975 | 50.131863419645 | | 1974 | 50.129568038866 | | 1973 | 50.129931553039 | | 1972 | 50.12808757819 | | 1971 | 50.125382621995 | | 1970 | 50.124786908953 | | 1969 | 50.124464172762 | | 1968 | 50.124724933018 | | 1967 | 50.123775409218 | | 1966 | 50.120134200753 | | 1965 | 50.117532603408 | | 1964 | 50.115663537398 | | 1963 | 50.110877803832 | | 1962 | 50.104734850496 | | 1961 | 50.099267629592 | | 1960 | 50.092991951409 |
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