| Year | Value | | 2021 | 70.290477827432 | | 2020 | 70.290477827432 | | 2019 | 70.290477827432 | | 2018 | 70.290477827432 | | 2017 | 70.290477827432 | | 2016 | 70.290477827432 | | 2015 | 70.290477827432 | | 2014 | 70.290477827432 | | 2013 | 70.290477827432 | | 2012 | 70.291081910295 | | 2011 | 70.291081910295 | | 2010 | 70.321903910307 | | 2009 | 70.321903910307 | | 2008 | 70.321903910307 | | 2007 | 70.318464765966 | | 2006 | 70.318464765966 | | 2005 | 70.318464765966 | | 2004 | 70.232486157444 | | 2003 | 70.232486157444 | | 2002 | 70.232486157444 | | 2001 | 70.232486157444 | | 2000 | 69.642672902982 | | 1999 | 67.923100732538 | | 1998 | 66.186332840389 | | 1997 | 64.466760669945 | | 1996 | 62.929463149568 | | 1995 | 62.729992777797 | | 1994 | 62.729992777797 | | 1993 | 62.747188499501 | | 1992 | 62.540839839048 | | 1991 | 62.506448395639 | | 1990 | 62.463459091378 | | 1989 | 62.411871926265 | | 1988 | 62.368882622004 | | 1987 | 62.31729545689 | | 1986 | 62.282904013481 | | 1985 | 62.23991470922 | | 1984 | 62.179729683255 | | 1983 | 62.136740378994 | | 1982 | 62.076555353028 | | 1981 | 62.033566048767 | | 1980 | 61.973381022801 | | 1979 | 61.938989579393 | | 1978 | 61.904598135984 | | 1977 | 61.782508511882 | | 1976 | 61.498779103759 | | 1975 | 61.490181242907 | | 1974 | 61.001822746501 | | 1973 | 60.941637720535 | | 1972 | 60.907246277126 | | 1971 | 60.855659112013 | | 1970 | 60.821267668604 | | 1969 | 60.786876225195 | | 1968 | 60.735289060082 | | 1967 | 60.692299755821 | | 1966 | 60.64931045156 | | 1965 | 60.606321147299 | | 1964 | 60.563331843037 | | 1963 | 60.520342538776 | | 1962 | 60.477353234515 | | 1961 | 60.434363930254 |
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