Year | Value | 2022 | 50.269011898603 | 2021 | 50.221681723419 | 2020 | 50.15904163015 | 2019 | 50.087954754112 | 2018 | 49.998595900028 | 2017 | 49.908738908876 | 2016 | 49.819558199529 | 2015 | 49.729005907459 | 2014 | 49.650638537312 | 2013 | 49.592248746355 | 2012 | 49.538339052646 | 2011 | 49.482732075868 | 2010 | 49.426223864497 | 2009 | 49.393717701264 | 2008 | 49.409863401257 | 2007 | 49.446398280446 | 2006 | 49.485211797993 | 2005 | 49.56574888185 | 2004 | 49.598364124719 | 2003 | 49.534482391291 | 2002 | 49.457679937847 | 2001 | 49.374079039945 | 2000 | 49.286123762622 | 1999 | 49.193986680054 | 1998 | 49.098027787701 | 1997 | 49.002739647157 | 1996 | 48.954362376645 | 1995 | 48.949179022639 | 1994 | 48.946042281219 | 1993 | 48.943820695873 | 1992 | 48.946108170212 | 1991 | 48.948932423509 | 1990 | 48.946768661431 | 1989 | 48.952389752593 | 1988 | 48.95205164214 | 1987 | 48.92656047695 | 1986 | 48.889721555065 | 1985 | 48.851611125722 | 1984 | 48.802908998118 | 1983 | 48.732324903797 | 1982 | 48.634900998243 | 1981 | 48.513592672471 | 1980 | 48.381213870887 | 1979 | 48.245285715258 | 1978 | 48.102050088805 | 1977 | 47.962614214968 | 1976 | 47.853532660852 | 1975 | 47.780030892892 | 1974 | 47.721724051384 | 1973 | 47.663299449722 | 1972 | 47.603130739828 | 1971 | 47.539143126096 | 1970 | 47.47346416536 | 1969 | 47.424806216082 | 1968 | 47.376941121731 | 1967 | 47.298403193613 | 1966 | 47.207371758694 | 1965 | 47.116652426611 | 1964 | 47.022150903709 | 1963 | 46.952825136124 | 1962 | 46.931869194378 | 1961 | 46.931416534768 | 1960 | 46.942242355606 |
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