| Year | Value | | 2021 | 66.402737047898 | | 2020 | 66.207233626589 | | 2019 | 65.620723362659 | | 2018 | 65.645161290323 | | 2017 | 65.818181818182 | | 2016 | 65.591397849462 | | 2015 | 65.004887585533 | | 2014 | 64.711632453568 | | 2013 | 64.516129032258 | | 2012 | 64.320625610948 | | 2011 | 63.636363636364 | | 2010 | 62.561094819159 | | 2009 | 64.809384164223 | | 2008 | 64.809384164223 | | 2007 | 66.187683284458 | | 2006 | 66.373411534702 | | 2005 | 63.831867057673 | | 2004 | 62.394916911046 | | 2003 | 61.290322580645 | | 2002 | 60.215053763441 | | 2001 | 58.455522971652 | | 2000 | 58.162267839687 | | 1999 | 56.940371456501 | | 1998 | 61.19257086999 | | 1997 | 60.801564027371 | | 1996 | 60.410557184751 | | 1995 | 59.530791788856 | | 1994 | 59.335288367546 | | 1993 | 59.237536656891 | | 1992 | 59.237536656891 | | 1991 | 59.237536656891 | | 1990 | 59.139784946237 | | 1989 | 59.042033235582 | | 1988 | 59.042033235582 | | 1987 | 59.042033235582 | | 1986 | 58.651026392962 | | 1985 | 58.553274682307 | | 1984 | 58.455522971652 | | 1983 | 58.455522971652 | | 1982 | 58.455522971652 | | 1981 | 58.455522971652 | | 1980 | 58.748778103617 | | 1979 | 59.921798631476 | | 1978 | 60.508308895406 | | 1977 | 61.094819159335 | | 1976 | 61.58357771261 | | 1975 | 62.072336265885 | | 1974 | 62.561094819159 | | 1973 | 63.049853372434 | | 1972 | 62.072336265885 | | 1971 | 61.58357771261 | | 1970 | 61.094819159335 | | 1969 | 60.606060606061 | | 1968 | 60.215053763441 | | 1967 | 59.237536656891 | | 1966 | 58.260019550342 | | 1965 | 58.260019550342 | | 1964 | 56.695992179863 | | 1963 | 55.718475073314 | | 1962 | 55.718475073314 | | 1961 | 54.936461388074 |
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