| Year | Value | | 2023 | 76.412 | | 2022 | 75.291 | | 2021 | 77.606 | | 2020 | 77.331 | | 2019 | 77.197 | | 2018 | 77.19 | | 2017 | 76.989 | | 2016 | 76.769 | | 2015 | 76.563 | | 2014 | 76.279 | | 2013 | 75.96 | | 2012 | 75.59 | | 2011 | 75.302 | | 2010 | 75.012 | | 2009 | 74.669 | | 2008 | 74.221 | | 2007 | 73.779 | | 2006 | 73.341 | | 2005 | 72.894 | | 2004 | 72.1 | | 2003 | 72.101 | | 2002 | 71.775 | | 2001 | 71.52 | | 2000 | 71.205 | | 1999 | 70.979 | | 1998 | 70.703 | | 1997 | 70.362 | | 1996 | 69.94 | | 1995 | 69.757 | | 1994 | 69.661 | | 1993 | 69.568 | | 1992 | 69.353 | | 1991 | 69.132 | | 1990 | 68.924 | | 1989 | 68.557 | | 1988 | 68.194 | | 1987 | 67.833 | | 1986 | 67.308 | | 1985 | 66.543 | | 1984 | 65.55 | | 1983 | 64.5 | | 1982 | 63.603 | | 1981 | 62.856 | | 1980 | 62.186 | | 1979 | 61.696 | | 1978 | 61.266 | | 1977 | 60.906 | | 1976 | 60.371 | | 1975 | 59.713 |
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