Year | Value | 2022 | 52.035435936585 | 2021 | 52.050497866287 | 2020 | 52.072905273733 | 2019 | 52.094010992933 | 2018 | 52.112353765625 | 2017 | 52.130650782451 | 2016 | 52.149837250448 | 2015 | 52.168956750323 | 2014 | 52.190145336999 | 2013 | 52.213533671645 | 2012 | 52.238800566262 | 2011 | 52.266902855317 | 2010 | 52.298233416208 | 2009 | 52.301938339829 | 2008 | 52.279421204174 | 2007 | 52.257187486185 | 2006 | 52.226680225571 | 2005 | 52.193322621226 | 2004 | 52.163274426919 | 2003 | 52.134400502432 | 2002 | 52.108235912255 | 2001 | 52.084393146354 | 2000 | 52.066259347004 | 1999 | 52.057387288488 | 1998 | 52.047852770044 | 1997 | 52.030589915813 | 1996 | 52.007473562842 | 1995 | 51.98453696679 | 1994 | 51.959787858409 | 1993 | 51.934328243836 | 1992 | 51.913055508585 | 1991 | 51.896670033385 | 1990 | 51.907922184279 | 1989 | 51.889596110667 | 1988 | 51.815567973659 | 1987 | 51.73784283251 | 1986 | 51.657313155552 | 1985 | 51.582134922512 | 1984 | 51.511005562055 | 1983 | 51.441882224518 | 1982 | 51.380054920553 | 1981 | 51.323208368017 | 1980 | 51.266489204377 | 1979 | 51.251119547901 | 1978 | 51.279037803425 | 1977 | 51.309565294016 | 1976 | 51.343820839994 | 1975 | 51.377230968473 | 1974 | 51.408780114785 | 1973 | 51.442305727121 | 1972 | 51.477462231679 | 1971 | 51.513513513514 | 1970 | 51.583076840226 | 1969 | 51.690399594337 | 1968 | 51.809257831225 | 1967 | 51.937401248966 | 1966 | 52.06923444615 | 1965 | 52.21124639242 | 1964 | 52.363258653741 | 1963 | 52.522734499205 | 1962 | 52.691532987834 | 1961 | 52.872082773494 | 1960 | 52.975704149645 |
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