| Year | Value | | 2021 | 65.130624092888 | | 2020 | 64.949201741655 | | 2019 | 64.949201741655 | | 2018 | 72.387518142235 | | 2017 | 72.931785195936 | | 2016 | 75.036284470247 | | 2015 | 75.036284470247 | | 2014 | 75.036284470247 | | 2013 | 75.036284470247 | | 2012 | 73.43976777939 | | 2011 | 72.895500725689 | | 2010 | 71.988388969521 | | 2009 | 65.904571843251 | | 2008 | 64.22351233672 | | 2007 | 64.22351233672 | | 2006 | 64.22351233672 | | 2005 | 64.22351233672 | | 2004 | 60.595065312047 | | 2003 | 60.595065312047 | | 2002 | 60.595065312047 | | 2001 | 60.595065312047 | | 2000 | 61.320754716981 | | 1999 | 61.320754716981 | | 1998 | 61.320754716981 | | 1997 | 61.320754716981 | | 1996 | 57.692307692308 | | 1995 | 57.692307692308 | | 1994 | 57.873730043541 | | 1993 | 57.148040638607 | | 1992 | 57.148040638607 | | 1991 | 57.910014513788 | | 1990 | 57.946298984035 | | 1989 | 57.982583454282 | | 1988 | 58.018867924528 | | 1987 | 58.055152394775 | | 1986 | 58.055152394775 | | 1985 | 58.055152394775 | | 1984 | 58.055152394775 | | 1983 | 58.055152394775 | | 1982 | 58.055152394775 | | 1981 | 58.055152394775 | | 1980 | 58.055152394775 | | 1979 | 57.873730043541 | | 1978 | 57.873730043541 | | 1977 | 57.510885341074 | | 1976 | 57.510885341074 | | 1975 | 57.43831640058 | | 1974 | 57.43831640058 | | 1973 | 57.43831640058 | | 1972 | 57.474600870827 | | 1971 | 62.046444121916 | | 1970 | 61.865021770682 | | 1969 | 61.683599419448 | | 1968 | 61.502177068215 | | 1967 | 61.320754716981 | | 1966 | 61.139332365747 | | 1965 | 60.957910014514 | | 1964 | 60.77648766328 | | 1963 | 60.595065312047 | | 1962 | 60.413642960813 | | 1961 | 60.232220609579 |
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