| Year | Value | | 2022 | 69.353400424886 | | 2021 | 69.534823005944 | | 2020 | 69.722908375092 | | 2019 | 69.952810878651 | | 2018 | 70.221141425284 | | 2017 | 70.492670287781 | | 2016 | 70.774692712455 | | 2015 | 71.072398599558 | | 2014 | 71.387618604947 | | 2013 | 71.718861172962 | | 2012 | 72.064608655842 | | 2011 | 72.425090712117 | | 2010 | 72.803085582009 | | 2009 | 72.794572109054 | | 2008 | 72.184080409977 | | 2007 | 71.196248899981 | | 2006 | 69.975917308062 | | 2005 | 69.035758759708 | | 2004 | 68.708692149602 | | 2003 | 68.625255445014 | | 2002 | 68.534794855318 | | 2001 | 68.433077663759 | | 2000 | 68.316351345039 | | 1999 | 68.181954652738 | | 1998 | 68.025592835649 | | 1997 | 67.840942071338 | | 1996 | 67.622394067014 | | 1995 | 67.446470566001 | | 1994 | 67.342371740266 | | 1993 | 67.242511527992 | | 1992 | 67.139220623835 | | 1991 | 67.030292528865 | | 1990 | 66.913734750554 | | 1989 | 66.785204036075 | | 1988 | 66.640177088178 | | 1987 | 66.474523592416 | | 1986 | 66.284196127588 | | 1985 | 66.484745595621 | | 1984 | 67.173062474252 | | 1983 | 67.966389026255 | | 1982 | 68.846672877478 | | 1981 | 69.818847824901 | | 1980 | 70.443213733472 | | 1979 | 70.630589178074 | | 1978 | 70.77347990825 | | 1977 | 70.837265035134 | | 1976 | 70.753870626871 | | 1975 | 70.516972951486 | | 1974 | 70.195444705308 | | 1973 | 69.777780797471 | | 1972 | 69.206968967908 | | 1971 | 68.410480881708 | | 1970 | 67.278351068826 | | 1969 | 65.637425422785 | | 1968 | 63.503010553324 | | 1967 | 62.208731269984 | | 1966 | 62.089540789769 | | 1965 | 61.940079518058 | | 1964 | 61.765826804997 | | 1963 | 61.568347706457 | | 1962 | 61.347958381751 | | 1961 | 61.087783010838 | | 1960 | 60.765517965014 |
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