| Year | Value | | 2021 | 70.274 | | 2020 | 72.561 | | 2019 | 72.242 | | 2018 | 72.553 | | 2017 | 72.417 | | 2016 | 71.592 | | 2015 | 70.8 | | 2014 | 69.782 | | 2013 | 69.682 | | 2012 | 69.764 | | 2011 | 69.914 | | 2010 | 69.894 | | 2009 | 69.505 | | 2008 | 68.816 | | 2007 | 68.204 | | 2006 | 67.571 | | 2005 | 67.002 | | 2004 | 66.416 | | 2003 | 65.596 | | 2002 | 65.531 | | 2001 | 65.482 | | 2000 | 65.508 | | 1999 | 65.443 | | 1998 | 65.594 | | 1997 | 65.697 | | 1996 | 65.668 | | 1995 | 65.337 | | 1994 | 65.272 | | 1993 | 64.98 | | 1992 | 64.65 | | 1991 | 64.453 | | 1990 | 64.23 | | 1989 | 64.01 | | 1988 | 63.437 | | 1987 | 63.186 | | 1986 | 62.96 | | 1985 | 63.058 | | 1984 | 62.872 | | 1983 | 62.593 | | 1982 | 62.455 | | 1981 | 62.251 | | 1980 | 62.034 | | 1979 | 61.878 | | 1978 | 61.684 | | 1977 | 61.453 | | 1976 | 61.25 | | 1975 | 61.049 | | 1974 | 60.841 | | 1973 | 60.697 | | 1972 | 60.507 | | 1971 | 60.392 | | 1970 | 60.402 | | 1969 | 60.224 | | 1968 | 60.062 | | 1967 | 59.905 | | 1966 | 59.691 | | 1965 | 59.485 | | 1964 | 59.625 | | 1963 | 59.039 | | 1962 | 58.474 | | 1961 | 57.767 | | 1960 | 57.102 |
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