| Year | Value | | 2022 | 49.4556615971 | | 2021 | 49.49247101059 | | 2020 | 49.538559460602 | | 2019 | 49.585907729282 | | 2018 | 49.635577132209 | | 2017 | 49.679530437566 | | 2016 | 49.717824108832 | | 2015 | 49.750174551247 | | 2014 | 49.775204782472 | | 2013 | 49.799046659294 | | 2012 | 49.82436969184 | | 2011 | 49.850583370815 | | 2010 | 49.875942982039 | | 2009 | 49.904666397344 | | 2008 | 49.938005285562 | | 2007 | 49.969745792358 | | 2006 | 49.99649657899 | | 2005 | 50.019267844411 | | 2004 | 50.038347992504 | | 2003 | 50.05782904053 | | 2002 | 50.075806536744 | | 2001 | 50.095246409364 | | 2000 | 50.114977941666 | | 1999 | 50.126165354304 | | 1998 | 50.132486980095 | | 1997 | 50.136205824914 | | 1996 | 50.137023078481 | | 1995 | 50.137954518705 | | 1994 | 50.140537566183 | | 1993 | 50.141521152838 | | 1992 | 50.137975188089 | | 1991 | 50.132580422614 | | 1990 | 50.127522843761 | | 1989 | 50.126228956739 | | 1988 | 50.128021352317 | | 1987 | 50.128942903885 | | 1986 | 50.129624130334 | | 1985 | 50.131218257077 | | 1984 | 50.134163192698 | | 1983 | 50.139094863375 | | 1982 | 50.146238837645 | | 1981 | 50.15412676442 | | 1980 | 50.162687569323 | | 1979 | 50.171433617813 | | 1978 | 50.180801322817 | | 1977 | 50.191396502032 | | 1976 | 50.200787078862 | | 1975 | 50.210175217228 | | 1974 | 50.22160450508 | | 1973 | 50.234225022785 | | 1972 | 50.247798368063 | | 1971 | 50.261727774069 | | 1970 | 50.27660225574 | | 1969 | 50.292721091493 | | 1968 | 50.310588162982 | | 1967 | 50.329833652647 | | 1966 | 50.350700276754 | | 1965 | 50.372930278243 | | 1964 | 50.394090147047 | | 1963 | 50.414941446164 | | 1962 | 50.437807185265 | | 1961 | 50.461605473775 | | 1960 | 50.487419481112 |
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