| Year | Value | | 2022 | 47.183640326302 | | 2021 | 47.178662837486 | | 2020 | 47.191516724489 | | 2019 | 47.208516526314 | | 2018 | 47.255782041209 | | 2017 | 47.325469826428 | | 2016 | 47.373647661954 | | 2015 | 47.423142395857 | | 2014 | 47.498869179541 | | 2013 | 47.588000804623 | | 2012 | 47.671868486914 | | 2011 | 47.753062852147 | | 2010 | 47.82613540987 | | 2009 | 47.89130141475 | | 2008 | 47.961347552585 | | 2007 | 48.018375946508 | | 2006 | 48.058255603902 | | 2005 | 48.093932377773 | | 2004 | 48.131261354307 | | 2003 | 48.172799442088 | | 2002 | 48.224709742598 | | 2001 | 48.249366866121 | | 2000 | 48.226457304634 | | 1999 | 48.1997766327 | | 1998 | 48.181049696864 | | 1997 | 48.166599855546 | | 1996 | 48.152834482181 | | 1995 | 48.138529663182 | | 1994 | 48.126172377528 | | 1993 | 48.124033549294 | | 1992 | 48.135206194287 | | 1991 | 48.153256198546 | | 1990 | 48.167885871039 | | 1989 | 48.178575224432 | | 1988 | 48.189270809743 | | 1987 | 48.194891859975 | | 1986 | 48.194551409795 | | 1985 | 48.192679007564 | | 1984 | 48.18732049173 | | 1983 | 48.176128673274 | | 1982 | 48.165213847872 | | 1981 | 48.155021045472 | | 1980 | 48.127058965881 | | 1979 | 48.078375185754 | | 1978 | 48.018214173667 | | 1977 | 47.950559662932 | | 1976 | 47.880801281773 | | 1975 | 47.807868313559 | | 1974 | 47.733981320549 | | 1973 | 47.656787929395 | | 1972 | 47.570706010665 | | 1971 | 47.483937452467 | | 1970 | 47.478307173577 | | 1969 | 47.551176981327 | | 1968 | 47.613440664701 | | 1967 | 47.664616867727 | | 1966 | 47.708939368129 | | 1965 | 47.740578476995 | | 1964 | 47.762767925379 | | 1963 | 47.78406372373 | | 1962 | 47.803190343158 | | 1961 | 47.82319489396 | | 1960 | 47.841045096808 |
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