| Year | Value | | 2022 | 48.862655540854 | | 2021 | 48.826533852753 | | 2020 | 48.833182661768 | | 2019 | 48.828366511891 | | 2018 | 48.812731273449 | | 2017 | 48.793096760186 | | 2016 | 48.771809855017 | | 2015 | 48.747373924406 | | 2014 | 48.727823190368 | | 2013 | 48.715219699417 | | 2012 | 48.699115945681 | | 2011 | 48.677563727632 | | 2010 | 48.658593172071 | | 2009 | 48.639543389536 | | 2008 | 48.62370847824 | | 2007 | 48.61471349562 | | 2006 | 48.605761139322 | | 2005 | 48.59710556184 | | 2004 | 48.586837672893 | | 2003 | 48.579500206164 | | 2002 | 48.577263829516 | | 2001 | 48.574321076932 | | 2000 | 48.58448227441 | | 1999 | 48.610804112663 | | 1998 | 48.637974366799 | | 1997 | 48.660943164607 | | 1996 | 48.679718469832 | | 1995 | 48.699522635246 | | 1994 | 48.721915797356 | | 1993 | 48.744621005555 | | 1992 | 48.771646046355 | | 1991 | 48.802248237102 | | 1990 | 48.836476881686 | | 1989 | 48.876479042035 | | 1988 | 48.915827800221 | | 1987 | 48.952217326319 | | 1986 | 48.983549325841 | | 1985 | 49.011487454462 | | 1984 | 49.042793596376 | | 1983 | 49.076131996547 | | 1982 | 49.106335099329 | | 1981 | 49.138588631401 | | 1980 | 49.167380897379 | | 1979 | 49.19014870714 | | 1978 | 49.21367793703 | | 1977 | 49.233122363742 | | 1976 | 49.245561641855 | | 1975 | 49.261725471437 | | 1974 | 49.281386345061 | | 1973 | 49.299472624954 | | 1972 | 49.320668133658 | | 1971 | 49.341569131511 | | 1970 | 49.363799554575 | | 1969 | 49.393985466871 | | 1968 | 49.421945117493 | | 1967 | 49.440872393781 | | 1966 | 49.459793216543 | | 1965 | 49.464846083807 | | 1964 | 49.461223925068 | | 1963 | 49.463280322943 | | 1962 | 49.463926955517 | | 1961 | 49.441001921828 | | 1960 | 49.388553864119 |
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