| Year | Value | | 2022 | 42.378703841542 | | 2021 | 42.236391498998 | | 2020 | 41.97630103997 | | 2019 | 41.843083506958 | | 2018 | 41.928671639919 | | 2017 | 42.009913572677 | | 2016 | 42.269735670678 | | 2015 | 42.674213327647 | | 2014 | 42.836349892565 | | 2013 | 42.796683414385 | | 2012 | 42.752781715049 | | 2011 | 42.699941908952 | | 2010 | 42.658949707107 | | 2009 | 42.689821163941 | | 2008 | 42.778062446476 | | 2007 | 42.866173678037 | | 2006 | 42.949374913081 | | 2005 | 43.026302047853 | | 2004 | 42.989542472832 | | 2003 | 42.889229927527 | | 2002 | 42.85529395098 | | 2001 | 42.842196042557 | | 2000 | 42.83647346616 | | 1999 | 42.828070516134 | | 1998 | 42.81962996359 | | 1997 | 42.81711595683 | | 1996 | 42.808872411938 | | 1995 | 42.790604005314 | | 1994 | 42.808863555292 | | 1993 | 42.845923345811 | | 1992 | 42.881117505287 | | 1991 | 42.951894156191 | | 1990 | 43.052839957705 | | 1989 | 43.174376305385 | | 1988 | 43.305902010471 | | 1987 | 43.449870608507 | | 1986 | 43.609269477487 | | 1985 | 43.798484823213 | | 1984 | 44.023907991 | | 1983 | 44.285766583064 | | 1982 | 44.575907089573 | | 1981 | 44.886601323012 | | 1980 | 45.236218885517 | | 1979 | 45.625119680826 | | 1978 | 46.047505885633 | | 1977 | 46.513902165097 | | 1976 | 47.00411896981 | | 1975 | 47.52928252125 | | 1974 | 47.91142012848 | | 1973 | 48.106001079456 | | 1972 | 48.297522701383 | | 1971 | 48.466433565778 | | 1970 | 48.601345748929 | | 1969 | 48.709811367046 | | 1968 | 48.802836678989 | | 1967 | 48.885863030582 | | 1966 | 48.95899801227 | | 1965 | 49.027018298338 | | 1964 | 49.092829600032 | | 1963 | 49.15375552697 | | 1962 | 49.209266042782 | | 1961 | 49.255024560804 | | 1960 | 49.282341906724 |
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