| Year | Value | | 2024 | 78.732 | | 2023 | 78.552 | | 2022 | 78.38 | | 2021 | 78.217 | | 2020 | 78.062 | | 2019 | 77.915 | | 2018 | 77.777 | | 2017 | 77.648 | | 2016 | 77.528 | | 2015 | 77.417 | | 2014 | 77.314 | | 2013 | 77.222 | | 2012 | 77.138 | | 2011 | 77.064 | | 2010 | 76.999 | | 2009 | 76.944 | | 2008 | 76.899 | | 2007 | 76.853 | | 2006 | 76.807 | | 2005 | 76.761 | | 2004 | 76.716 | | 2003 | 76.67 | | 2002 | 76.624 | | 2001 | 76.578 | | 2000 | 76.532 | | 1999 | 76.485 | | 1998 | 76.439 | | 1997 | 76.393 | | 1996 | 76.347 | | 1995 | 76.3 | | 1994 | 76.254 | | 1993 | 76.207 | | 1992 | 76.161 | | 1991 | 76.114 | | 1990 | 75.957 | | 1989 | 75.753 | | 1988 | 75.548 | | 1987 | 75.341 | | 1986 | 75.134 | | 1985 | 74.925 | | 1984 | 74.715 | | 1983 | 74.504 | | 1982 | 73.942 | | 1981 | 73.028 | | 1980 | 72.096 | | 1979 | 71.141 | | 1978 | 70.169 | | 1977 | 69.178 | | 1976 | 68.17 | | 1975 | 67.142 |
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