| Year | Value | | 2022 | 49.843594690292 | | 2021 | 49.858890426134 | | 2020 | 49.87437662003 | | 2019 | 49.88406830841 | | 2018 | 49.891009708582 | | 2017 | 49.898365466702 | | 2016 | 49.907070243712 | | 2015 | 49.91679166892 | | 2014 | 49.92630472462 | | 2013 | 49.937803697529 | | 2012 | 49.947891809297 | | 2011 | 49.957775002515 | | 2010 | 49.970198125156 | | 2009 | 49.983371511068 | | 2008 | 49.995374424739 | | 2007 | 50.007151469075 | | 2006 | 50.02236824718 | | 2005 | 50.039015482074 | | 2004 | 50.054097695718 | | 2003 | 50.068754339393 | | 2002 | 50.087783577279 | | 2001 | 50.178047554671 | | 2000 | 50.33352372204 | | 1999 | 50.490814703984 | | 1998 | 50.569492717767 | | 1997 | 50.566251246112 | | 1996 | 50.567438194066 | | 1995 | 50.503839787416 | | 1994 | 50.480615478361 | | 1993 | 50.589490773917 | | 1992 | 50.715477474736 | | 1991 | 50.766932163328 | | 1990 | 50.758937350734 | | 1989 | 50.754526028402 | | 1988 | 50.742544533971 | | 1987 | 50.727078335839 | | 1986 | 50.710855739356 | | 1985 | 50.699024333701 | | 1984 | 50.690205875047 | | 1983 | 50.678749073789 | | 1982 | 50.664590009064 | | 1981 | 50.654971062422 | | 1980 | 50.651460417625 | | 1979 | 50.64655195349 | | 1978 | 50.638668493902 | | 1977 | 50.631321224632 | | 1976 | 50.625009725832 | | 1975 | 50.615976320354 | | 1974 | 50.60637535878 | | 1973 | 50.596906611764 | | 1972 | 50.586953378729 | | 1971 | 50.57188394127 | | 1970 | 50.556047472723 | | 1969 | 50.544413168763 | | 1968 | 50.526563500249 | | 1967 | 50.497875868112 | | 1966 | 50.458280788438 | | 1965 | 50.409888487075 | | 1964 | 50.35589899229 | | 1963 | 50.298375372225 | | 1962 | 50.215916513172 | | 1961 | 50.156368998428 | | 1960 | 50.148184314755 |
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